The following definitions include all S-registers defined for the various families of Hayes modems. Some factory settings and ranges are included here because they are almost universally implemented with these values; however, be sure to consult the user documentation that came with your modem for the S-registers and their ranges/factory settings that your modem supports. Note that S-register numbers not included in this listing are those for which no function has been assigned.
S0 Ring to Answer After
S0 sets the ring number on which the modem automatically answers a call when auto-answer mode is selected. S0=0, the factory setting, disables auto-answer.
S1 Ring Count
When the modem is in the command state and set for auto-answer (S0>0), the modem automatically tracks the number of times the phone rings, incrementing and writing the value in S1. The value reverts to 0 if no ring occurs for 8 seconds. Once a connection is made, the modem resets the value of S1 to 0. Note that two short ring bursts within a ring cycle are counted as two rings.
S2 Ecape Sequence Character
S2 holds the ASCII value of the escape sequence character. The factory-set value is ASCII 43, the plus sign (+). The value for this register can be set to any ASCII value between 0 and 127. Setting S2 to a value greater than 127 disables the escape sequence, preventing the modem from returning to the command state and disabling command recognition.
S3 Carriage Return Character
S3 holds the ASCII value of the line terminating character. The factory-set value is ASCII 13 - carriage return (<CR>) - the range for theregister is 0-127. This character is used both as the command line terminator and the result code terminator.
S4 Line Feed Character
S4 holds the ASCII value of the line feed character. The factory setting is 10; the range is 0-127.
S5 Backspace Character
S5 holds the ASCII value of the backspace character. The factory-set value is ASCII 08; the range for the register is 0-32, 127. This character moves the cursor left, removing the previous character. As this value actually represents the combined operation of three characters (a backspace, a space, and another backspace), the time allotted to process the backspace character must not be any less than the time required by the modem to transmit three characters. For this reason, a repeat-key function may not operate properly on backspaces.
S6 Wait Before Blind Dialing
S6 determines how long the modem waits after going off-hook before it dials. This delay allows time for the central telephone office to detect the off-hook condition of the line and apply dial tone. This wait time only applies to the first dial tone. S6 is used only if X0, X1, or X3 is selected. Selecting X2 or X4 enables dial tone (call progress) detection and disables blind dialing, thus making the setting of S6 irrelevant. The value of this register can be set for any number from 4 through 7 seconds. This feature allows you to increase the time delay if you have difficulty obtaining dial tone within 4 seconds. Note: The Wait Before Dialing call progress monitoring feature (W dial modifers) applies only to detection of a second dial tone and is independent of any S-register setting.
S7 Wait for Carrier after Dialing
S7 determines the modem's time delay between dialing and responding to an incoming carrier signal after initial connection. If the modem does not detect a carrier within this time, the modem hangs up and returns the NO CARRIER result code. If the modem detects a carrier within the specified time, it goes on line.
S8 Duration of Delay for Comma Dial Modifier
S8 determines the duration of the delay generated by the comma (,) dial modifier.
S9 Carrier Detect Response Time
S9 determines how many seconds a carrier signal must be present for the modem to recognize it and issue a carrier detect. The value for the register is measured in tenths of a second. The factory setting is 6 (0.6 second); the range is 1 (0.1 second) to 255 (25.5 seconds). Note: The S9 value affects the time required to recognize the presence of carrier only if X3 or X4 is selected. The modem also ignores the value in register S9 when operating in half-duplex synchronous or asynchronous mode.
S10 Delay Between Lost Carrier and Hang Up
S10 specifies the time between loss of remote carrier and local modem disconnect. The delay permits the carrier to disappear momentarily without causing the modem to hang up. The value for the register is measured in tenths of a second. The range for most modems is 1 (0.1 second) to 255 (25.5 seconds).
The modem recognizes a carrier after the period of time specified in S9. Therefore, if the value of S10 is less than that set for S9, even a momentary loss of carrier will cause the modem to disconnect. Setting the register to 255 causes the modem to ignore actual carrier status and assume a carrier is always present. When operating in half-duplex synchronous mode, S10 specifies the maximum time (in seconds) that a carrier may be continuously present or absent before causing the modem to disconnect.
S11 Multi-Frequency Tone Duration
S11 determines the duration and spacing of tones in multi-frequency tone dialing. The value in this register has no effect on the speed of pulse dialing.
S12 Escape Sequence Guard Time
S12 holds the value of the delay required prior to and following the escape sequence. The guard time also dictates how quickly the escape sequence characters must be entered, since the interval between entry of each of the three characters must be of shorter duration than that specified for the guard time. If guard time is set to 0, timing is not a factor.
S18 Modem Test Timer
S18 establishes the duration of the modem's diagnostic tests. When a test is active for a length of time equal to the value chosen for this register, the modem automatically terminates the test. A setting of zero (0) disables the test timer (factory setting). The range for this register is 0-255 seconds.
S25 DTR Detection
S25 serves two purposes. When the modem is operating in synchronous mode 4, the value assigned to S25 specifies the length of time the modem waits after a connection has been made, before examining the DTR circuit. This allows the modem to ignore an on-to-off transition of DTR and gives the user sufficient time to disconnect the modem from the asynchronous terminal and attach it to a synchronous terminal, without forcing the modem back to the asynchronous command state. During this time, the value of S25 is read in full seconds (e.g., the factory-set value of 5 equals 5 seconds, instead of 0.05 seconds).
In all other modes, and after call establishment in synchronous mode 4, the value is read in 1/100 seconds. In any mode, a change in DTR (on or off) that persists for a period shorter than the value held in S25 is ignored by the modem while it is on-line. The range of values for S25 is 0-255.
S26 RTS to CTS Interval
S26 is used to specify the interval to delay before turning on CTS after an off-to-on transition of RTS. This value takes effect when the &R0 command option has been selected. This setting applies to synchronous modes 1, 2, and 3 only. The factory-set value is 1 (.01 seconds) with a range of 0-255.
S30 Inactivity Timeout
S30 monitors the line to prevent unnecessary connection time. If no data transfer is detected (while the modem is in the on-line state) for a duration specified by this register, the modem hangs up and returns to the idle state. When the value of S30 is set to 0, the timer is disabled. The factory setting is 0 seconds; the range is 0-255 units of 10 seconds. Note that S30 is only effective in &Q0, &Q5 or &Q6 modes; it is not enabled in any synchronous modes.
S33 AFT Options
Register S33 applies only to communications using a V-series Modem Enhancer with a Smartmodem 1200 which has an asynchronous DTE link.
This register selects the options to be used with Hayes Asynchronous Framing Technique (See the description of S44). AFT offers options to prevent certain characters (like XON and XOFF) from being sent. Normally AFT uses all 256 ASCII character codes; that is, it uses characters with 8 data bits. If intervening equipment is limited to 7-bit operation, the Eight-Bit Data Transparency option (S33=4) can be enabled.
With this option, AFT limits itself to using characters with 7 data bits. This pertains only to the communication link between the two modems, not to the format of the data. The data itself is unaffected by enabling any AFT transparency options.
0 No transparency options required (factory
setting).
1 Flow Control Transparency. AFT makes
transparent the XON and XOFF
control characters sent from the
DTE to the modem. The XON and
XOFF characters themselves are not
sent over the communication
link; characters that substitute
for these functions are
transmitted, instead.
2 Select Control Character Transparency.
4 Select Eight-Bit Data Transparency.
5 Select both Flow Control Transparency
and Eight-Bit Data
Transparency.
6 Select both Control Character Transparency
and Eight-Bit Data
Transparency.
If feature negotiation is active, the transparency option selected by one modem is used by both modems.
S36 Negotiation Failure Treatment
When an attempt to make an error-control connection fails, the modem reads this register to determine whether to terminate the connection, make an asynchronous connection (otherwise selected with &Q0), or make an asynchronous connection with ASB (otherwise selected with &Q6). This register is referenced only when the error-control mode has been selected with the &Q5 command (factory setting) and this communication mode cannot be negotiated.
0 Hang up.
1 Attempt a standard asynchronous connection
(&Q0).
3 Attempt an asynchronous connection using
automatic speed buffering
(&Q6).
4 Attempt a V.42 Alternative Protocol connection
(MNP compatible);
if negotiation fails, hang up.
5 Attempt a V.42 Alternative Protocol connection
(MNP compatible);
if negotiation fails, attempt a
standard asynchronous connection.
6 Attempt a V.42 Alternative Protocol connection
(MNP compatible);
if negotiation fails, hang up.
7 Attempt a V.42 Alternative Protocol connection
(MNP compatible);
if negotiation fails, attempt an
asynchronous connection using
automatic speed buffering (ASB).
In asynchronous mode, the CONNECT XXXX message will be returned with a successful connection. This message indicates the speed of the connection, which is also the speed of data transmitted from computer to modem.
Note: The selected fallback option can be initiated immediately with S48. For example, a connection attempt using the Alternative Protocol can be forced by setting S48=128 and S36=5 or 7.
The following table shows the order in which the bits of S36 are evaluated: (Remember, these steps only occur after the S46/S48 selections have failed to make a LAPBased error-controlled connection in &Q5 mode.)
S36 Bit 7-3=0 reserved
First Bit 2 (4) If set, means try MNP protocol;
reset means
don't use
MNP.
Third Bit 1 (2) If set, means fall back
to ASB; reset means
direct async.
Second Bit 0 (1) If set, means fall back based
on Bit 1; reset
means hang
up.
Also see Appendix D,"Establishing the Desired Connection and Fallback Strategy."
S37 Desired DCE Line Speed
The modem attempts to connect with a remote modem at the highest supported DCE speed that does not exceed the value specified by this register. If S37 is set to a speed higher than that supported by the modem, it will attempt to connect at its highest capability. Note that this is the speed of modems across the telephone line, not the speed at which the modem communicates with the attached DTE.
0 Attempt to connect at highest line speed
that does not exceed
the speed of last AT command issued.
1 Attempt to connect at 75 bps
2 Attempt to connect at 110 bps
3 Attempt to connect at 300 bps
4 Reserved
5 Attempt to connect at 1200 bps
6 Attempt to connect at 2400 bps
7 Attempt to connect at 4800 bps
8 Attempt to connect at 7200 bps
9 Attempt to connect at 9600 bps
10 Attempt to connect at 12000 bps
11 Attempt to connect at 14400 bps
S38 Delay Before Forced Hang up
S38 specifies the delay between the modem's receipt of the command to hang up (or on-to-off transition of DTR if the modem is configured to follow the signal) and the disconnect operation. This register is useful for error-control communications to ensure that data in the modem buffers is sent before the connection is terminated. The factory setting is 20 (seconds).
If this register is set between 0 and 254, the modem will wait that number of seconds for the remote modem to acknowledge receipt of all data in buffers before hanging up. If this timeout occurs before all data can be sent, the NO CARRIER (3) result code will be sent to indicate that data has been lost. If all data is transmitted prior to the timeout, the response to the H0 command will be OK.
If S38 is set to 255, the modem does not timeout, and continues to attempt to deliver data in buffers until the connection is lost, or the data is delivered.
S43 Current DCE Speed
The value in S43 indicates the DCE speed of the last carrier established. This is a read-only register.
0 No connection
1 Reserved
2 110 bps
3 300 bps
4 Reserved
5 1200 bps
6 2400 bps
7 4800 bps
8 7200 bps
9 9600 bps
10 12000 bps
11 14400 bps
S44 Asynchronous Framing Technique Selection
Register S44 applies only to communications using a V-series Modem Enhancer with a Smartmodem 1200 that connects using an asynchronous link across the telephone line. S44 sets the use of the Hayes Asynchronous Framing Technique. Connections to a packet-switched network or between two error-control modems using either Error-control/LAPB or X.25 protocol are usually synchronous connections, even though the user interface is always asynchronous.
Some environments may require asynchronous to synchronous conversion in the protocol because equipment is limited to asynchronous operation, or an asynchronous to synchronous conversion is already in place. For example, most Hayes 1200 bps modems support only asynchronous communication over the telephone line. When one of these modems is connected to a V-series Modem Enhancer, the interface between the two is always asynchronous. A feature provided by the V-series Modem Enhancer called the Asynchronous Framing Technique (AFT) makes this possible. When AFT is enabled, the output of the error-control protocol is asynchronous instead of synchronous. The values of S44 are as follows:
2 Use AFT. When AFT is selected, the data
output is asynchronous
instead of synchronous. AFT is required
if the path your call
takes passes through asynchronous-only
equipment.
3 The modem automatically selects whether
or not to use AFT.
V-series Modem Enhancer, when connected
to a Smartmodem 1200,
automatically uses AFT (factory
setting).
If the modem is configured to use feature negotiation, and the other modem is using AFT, both modems automatically select AFT.
S46 Error-control Protocol Selection
S46 specifies the error-control method used for subsequent connections.Because the factory setting will be a protocol for point-to-point communications, other connections, such as the X.25 protocol must be enabled by setting S46.
Feature negotiation enables two communicating modems to identify the common protocols, and chooses one based on the user-configuration for the communication session. For example, if an ULTRA product is configured to use the X.25 protocol, but connects with a V-series product without X.25 capability, an error-control protocol is automatically selected because both modems support it. However, if aULTRA product with X.25 connects with another ULTRA product with X.25, both can use X.25 protocol if configured to do so (S46=6).
When attempting a connection to a packet-switched network, automatic feature negotiation is usually disabled because unless an X.25 connection can be made, further network connections cannot be made. To disable automatic feature negotiation and make an X.25 connection or hang up, set S46=134. The options for this register are described below:
0 Either LAPM or fallback to LAPB
1 LAPB only
2 LAPM or fallback to LAPB; use data compression*
3 LAPB with data compression*
6 X.25 or fallback to LAPB; use data compression*
134 X.25
136 LAPM only
138 LAPM with data compression*
* Note: The technique negotiated is determined by capabilities and configuration of both modems. V.42bis is attempted first, then Hayes Adaptive Data Compression. If neither method is supported by both modems, or if either modem has compression disabled, no compression will be used.
S48 Enabling/Disabling Feature Negotiation
S48 selects how feature negotiation is used when making connections with the remote system. The negotiation process can be tailored to suit a connection, or bypassed altogether. For example, when the capabilities of the remote modem are known, negotiation is unnecessary. The factory setting is 7, negotiation enabled. With feature negotiation disabled, the modem assumes that the remote modem is configured the same as itself, and proceeds to activate the error-control protocol specified by the S46 (protocol options) setting. Use 128 when calling a packet-switched network that does not support feature negotiation.
0 Negotiation disabled; presume the remote
modem is configured for
and has the capabilities necessary
for the connection selected
with S46.
3 Negotiation enabled, but originating
modem remains silent during
detection phase. For connections
with MNP modems; however, this
setting defeats the negotiation
sequence with other V.42 modems.
7 Negotiation enabled.
128 Negotiation disabled; forces fallback options specified
in S36
to be taken immediately.
S49 ASB buffer size lower limit
S49 sets the lower limit of the modem's buffer when communicating in asynchronous mode with ASB. The range of this register is 1-249. The factory setting is 8 bytes.
S50 ASB buffer size upper limit
S50 sets the upper limit of the modem's buffer when communicating in asynchronous mode with ASB. The range of this register is 2-250 bytes. The factory setting is 16 bytes.
S53 Global PAD Configuration
S53 defines a set of behavior switches that control the PAD and all four channels in the Hayes product. This fixed user interface provides software and users with a consistent PAD command interface regardless of current PAD parameter settings. The fixed user interface is effective in all states except the on-line (data transfer) state.
For example, the factory-set value of PAD parameter 2 is zero, which turns off character echo. This is required for a transparent on-line state (e.g., for Smartmodem product emulation). However, since it may be difficult to enter PAD commands without seeing them echoed at your terminal, a method of controlling the PAD despite the parameter settings would be necessary.
The fixed user interface affects the following in all states, except the on-line state:
* Transmission of all PAD result codes, including the prompt PAD
result
code.
* Echo control via the E command.
* Fixed editing characters (delete character is defined by S5,
delete
line character is Control-X, line display character is
Control-R).
* Echo mask masks only the editing characters.
The fixed PAD control interface affects the following in all states:
* Disables PAD recall using a character (PAD parameter 1) or a
break
signal.
* Disables all PAD flow control (PAD parameters 5, 12).
* Disables carriage return (PAD parameter 9) and line feed (PAD
parameter 14) padding.
* Disables line folding (PAD parameter 10).
* Existing result codes use result codes for terminal (PAD parameter
19).
* Disables page wait (PAD parameter 22).
* Disables execution of ANS and EXEC strings.
* Disables EXEC command.
If the value of S53 includes any bit value except 1, the PAD prompt
character changes from * to -. The change in the prompt PAD character
provides an indication that the PAD is not in CCITT mode. The register's
values are provided below:
------------------------------------------------------------------------
0 Normal CCITT-compatibility mode.
1 Normal CCITT-compatibility mode. PAD prompt
is an asterisk (*) and
appears with the channel number (e.g.,
1*).
2 Fixed user interface. PAD prompt is a hyphen
(-).
3 Fixed user interface. PAD prompt is a hyphen
and appears with the
channel number (e.g., 1-) (factory setting).
4 Fixed control interface. PAD prompt is a
hyphen.
5 Fixed control interface. PAD prompt is a
hyphen and appears with
the channel number.
6 Fixed user and fixed control interface. PAD
prompt is a hyphen.
7 Fixed user and fixed control interface. PAD
prompt is a hyphen and
appears with the channel number.
------------------------------------------------------------------------
S55 AutoStream Protocol Request
S55 allows the user to request one of the AutoStream levels. The range
is 0 to 3 with a factory setting of 0.
Parameter Description
Value
-------------------------------------------------------------------
0
No AutoStream.
1
Request AutoStream Level 1 (allows multiplexing of multiple
virtual channels on the DTE).
2
Request AutoStream Level 2 (allows transparent control over
one PAD at a time - non simultaneous).
3
Request AutoStream Level 3 (allows transparent control over
all PADs simultaneously).
------------------------------------------------------------------------
S56 AutoStream Protocol Status
S56 reflects the status of the current AutoStream level. An alternative
to reading this register is examining the extended result codes (see
W1). The range is 0 to 3 with a factory setting of 0. This register
applies to Hayes modems that support X.25 and AutoStream.
Parameter Description
Value
------------------------------------------------------------------------
0 Indicates
no AutoStream.
1 Indicates
AutoStream Level 1 (allows multiplexing of
multiple virtual channels on the DTE).
2 Indicates
AutoStream Level 2 (allows transparent control
over one PAD at a time - non simultaneous).
3 Indicates
AutoStream Level 3 (allows transparent control
over all PADs simultaneously).
------------------------------------------------------------------------
S57 Network Options Register
This bit-mapped register allows configuration of the packet layer for
operation with different networks. This register applies to Hayes modems
that support X.25 and AutoStream.
Bit 0: Address may be sent in the call accept or clear request
packets.
Otherwise, the address length is set to zero.
Bit 1: Neither address, facility, nor data fields may be set in
call
accept or clear request packets. Address is not sent, even if used
in
combination with bit value 1.
------------------------------------------------------------------------
S57=0 In call accept or clear request packets,
the address length is
set to zero,
but facility and data fields may be present
(factory setting).
S57=1 In call accept or clear request packets,
address, facility, or
data fields
may be present.
S57=2, 3 In call accept or clear request packets, no fields may
be
sent.
------------------------------------------------------------------------
S63 Private Circuit (Leased Line) Carrier Level Adjustment
S63 selects the carrier power level in dBm for leased line operation.
This register specifies a nominal carrier level value. The range for
this register is 0-15 (0 dBm to -15 dBm). The factory setting is 0.
Note
that for those modems supporting leased line operation, carrier level
(if adjustable) may be set by other means. Please refer to the modem's
installation information for details.
S69 Link Layer Window Size
S69 sets the number of frames (packets) sent between acknowledgements
from the remote system. Each frame is one packet and the window size
is
how many frames you can send before you must stop and wait for the
remote end to send an acknowledgement that it received the frames and
is
ready to receive more frames. The range is 1-15 with a factory setting
of 15. LAPM connections use a window size of 1-15; LAPB connections
and
X.25 connections use a window size of 1-8. If a LAPB or X.25 connection
is made, any value greater than 8 is treated as 8.
Reducing window size can reduce performance. Reduce the window size
only
when so instructed by the network (this rarely occurs).
S70 Maximum Number of Retransmissions
S70 limits the number of times the modem will retransmit a frame.
Retransmissions become necessary when data errors introduced by noise
disrupt the reception of a frame. When the limit set by S70 is reached,
the modem hangs up. Raising this limit may be necessary if, for example,
telephone lines are extremely noisy. The retransmission delays may
be
undesirable, but the modem will not hang up. The range for this register
is 0-255, with a factory setting of 10.
S71 Link Layer Timeout
When the link layer sends a character, it starts a timer referenced
in
the formula below as "T1." If the remote end does not respond
after T1
seconds, the link layer retransmits. The value of T1 is computed
automatically based on the connection speed and maximum packet size.
T1 = 2 * (maximum packet size + 11) * (8 V bits per second) + T2 + 500
msec
The S71 setting is represented by the "T2" in the formula. The setting
affords some control over the final value of T1. You can increase T1
by
increasing T2. You may want to do this if your communication environment
has unusually long delays transmitting information from one end to
the
another (such as with satellite connections), or if the computer at
the
other end takes a long time to respond. The range for this register
is
1-255 milliseconds, with a factory setting of 20.
S72 Loss of Flag Idle Timeout
A transmitter not currently sending data to send is described as "idle."
Normally, idle transmitters send a repeating pattern called "flag idle."
Your modem always monitors the line to make sure the remote end of
the
communication link is either sending data or a flag idle. This ensures
that the modem is operating. S72 determines how long the local modem
waits before hanging up when it no longer is receiving data or a flag
idle.
In some systems, periods of "mark idle" (periods where all ones are
transmitted instead of the flag pattern) are normal. When using such
a
system, it may be necessary to increase the value in S72. If the
register is set to 0, this monitoring function is disabled. The range
for this register is 1-255 seconds; the factory setting is 30.
S73 No Activity Timeout
If your modem is receiving good carrier and flag idle from the remote
modem but does not receive any data for the time period specified by
S73, it will send a query (called an "RR") to the remote modem to make
sure the modem is operating properly.
The range for this register is 1-255 seconds; the factory setting for
this register is 5. Decreasing this value causes the modem to test
more
frequently for malfunctions at the remote end. However, the modem will
not hang up for approximately 2 * T1 * N2 seconds because it retransmits
the RR query several times.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1.3.1 Logical Channel Number Selectors - PS74,
S75, S76, S77, S78, S79
Although Hayes products supporting X.25 support four virtual channels,
numbered 1 through 4, packet-switched networks can support up to 4096
channels (numbered 0-4095). Each network has its own channel numbering
system to support multiple users. For example, if there are 15 calls,
each with four virtual connections, the packet-switched network can
support
all 60 (4*15) virtual calls, but each has to have a different logical
channel number.
Networks often set up their system so that all incoming calls are within
one range and all outgoing calls are within another range. Logical
Channel Numbers are automatically assigned by the Hayes product, but
the ranges need to be configurable in order to be compatible with
different network requirements.
S74, S75 Minimum Incoming Logical Channel Number (LCN)
S74 and S75 combine to specify the lowest incoming Logical Channel
Number the packet layer will report or accept. The value used is formed
by using S74 as the two high decimal digits and S75 as the two low
decimal digits, or the value can be expressed by the formula
S74*100+S75. If the resulting value is outside the range (0-4095),
the
value is assigned to the appropriate corresponding limit (e.g., if
a
value of 4099 is used, it is assigned to the upper limit value of 4095).
------------------------------------------------------------------------
S74=0 Factory setting from a range of 0-40
S75=1 Factory setting from a range of 0-99
------------------------------------------------------------------------
S76, S77 Maximum Incoming Logical Channel Number (LCN)
S76 and S77 combine to specify the highest incoming Logical Channel
Number the packet layer will report or accept. The value used is formed
by using S76 as the high two decimal digits and S77 as the two low
decimal digits, or the value can be expressed by the formula
S76*100+S77. If the resulting value is outside the range (0-4095),
the
value is assigned to the appropriate corresponding limit (e.g., if
a
value of 4099 is used, it is assigned to the upper limit value of 4095).
------------------------------------------------------------------------
S76=40 Factory setting from a range of 0-40
S77=95 Factory setting from a range of 0-99
------------------------------------------------------------------------
S78, S79 Outgoing Logical Channel Number (LCN)
The setting of registers S78 and S79 should be adjusted if the network
requires a range of Logical Channel Numbers outside those specified
with
the combination of these two registers. S78 and S79 combine to determine
the outgoing Logical Channel Number the packet layer will use to place
a
call. The value is derived using S78 as the two high decimal digits
and
S79 as the low two decimal digits, or the value can be expressed by
the
formula S78 * 100 + S79.
If the resulting value is outside the range (4-4095), the value is then
assigned to the appropriate limit. The highest Logical Channel Number
would be that derived from the above formula, and the lowest would
be the
value minus the maximum number of channels supported plus one.
The user has the ability to override this factory setting and explicitly
specify an LCN using the PAD selection command (CALL).
------------------------------------------------------------------------
S78=0 Factory setting from a range of 0-40
S79=16 Factory setting from a range of 0-99
------------------------------------------------------------------------
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1.3.2 Packet Layer Parameters - PS80, S81
The values in S80 and S81 combine to set time and duration for packet
layer restart requests.
S80 Packet Layer N20 Parameter
S80 sets the maximum number of times a restart request can be
retransmitted. The factory setting is 1 (S80=1) from a range of 0-255.
Setting this register may be necessary if the network requires a restart
attempt to abandon a connection earlier than planned.
S81 Packet Layer T20 Parameter
S81 sets the maximum amount of time the transmitter will wait for
acknowledgment of a restart request frame before initiating a recovery
procedure, in 10-second increments. The factory setting is 18 from
a
range of 0-255. Setting this register may be necessary if the network
requires a restart attempt to abandon a connection earlier than planned.
S82 Break Signaling Technique
S82 selects a method of break signal handling for V.42 communications:
in sequence, expedited, and destructive. Break signals provide a way
for
you to get the attention of the remote host. The break type used depends
on your application. The values for S82 are:
------------------------------------------------------------------------
3 Expedited signaling regardless of its sequence
in data sent and
received; data integrity maintained.
7 Destructive signaling regardless of its sequence
in data sent and
received; data in process at time is
destroyed.
128 In sequence signaling as data is sent and received;
data
integrity maintained ahead of and after
break.
------------------------------------------------------------------------
S84 Adaptive Start Up (ASU) negotiation
S84 selects the adaptive start up (ASU) method to be negotiated for
subsequent connections.
------------------------------------------------------------------------
0 Do not negotiate ASU connection.
126 Negotiate ASU with fixed start up.
129 Negotiate ASU with fast start up on both sides.
130 Negotiate ASU with smooth start up on both sides.
131 Negotiate ASU with configuring modem using fast start
up and the
other modem using smooth start up.
132 Negotiate ASU with configuring modem using smooth start
up and the
other modem using fast start up.
------------------------------------------------------------------------
S85 ASU Negotiation Report
S85 indicates whether adaptive start up and method were negotiated for
the current connection. To read S85, issue the escape sequence to place
the modem in the command state, then issue ATS85? <CR>. The modem
will
report one of the values below.
------------------------------------------------------------------------
0 ASU not negotiated; fixed start
up in use.
126 ASU negotiated with fixed start up.
129 ASU negotiated with fast start up on both
sides.
130 ASU negotiated with smooth start up on
both sides.
131 ASU negotiated with reporting modem using
fast start up and the
other modem using smooth
start up.
132 ASU negotiated with reporting modem using
smooth start up and
the other modem using fast
start up.
------------------------------------------------------------------------
S86 Connection Failure Cause
S86 can help you determine the cause of a connection failure. When the
modem issues a NO CARRIER result code, a value is written to this
register. To read this register, following the connection failure,
issue
ATS86? <CR>. The modem will report one of the values below.
------------------------------------------------------------------------
0 Normal hang up; no error occurred.
4 Physical carrier loss.
5 Feature negotiation failed to detect
presence of another
error-control modem at the other
end.
6 Other error-control modem did not respond
to feature negotiation
message sent by this modem.
7 Other modem is synchronous-only; this
modem is asynchronous-only.
8 Modems could not find a common framing
technique.
9 Modems could not find a protocol in
common.
10 Feature negotiation message sent by other
modem incorrect.
11 Synchronous information (data or flags)
not received from other
modem. Modem waited 30 seconds
before hanging up.
12 Normal disconnect initiated by other modem.
13 Other modem did not respond after many transmissions
of the same
message. Modem made 10 attempts
then hung up.
14 Protocol violation occurred.
15 Compression failure.
------------------------------------------------------------------------
Note: Multiple occurrences may contribute to a NO CARRIER message;
S86
records the first event that occurred.
S87 Fixed Speed DTE Interface (Default High AT Speed)
The modem always accepts AT commands up to and including 9600 bps. Above
9600 bps, the S87 setting determines which additional speed will be
available for autobauding. (Autobauding is the process by which a modem
determines the DTE speed from the A (and possibly T) of an AT command).
Refer to the description of the r2-string in the I command description.
The following list identifies the possible values of S87. The factory
default value is the lowest available value in the modem. Refer to
the
user documentation supplied with your modem to determine if S87 is
supported by your modem and which values of S87 it supports.
Value Indicated Speed
------------------------------------------------------------------------
14 19200
28 38400
------------------------------------------------------------------------
S91 PSTN Transmit Level Adjustment
The PSTN (Public Switched Telephone Network) line transmit level can
be
adjusted using register S91. This register specifies a carrier level
value that is not to be exceeded. The allowable range for register
S91
is listed in your modem's user documentation.
S92 MI/MIC Options
S92 enables and selects or disables the mode indicate/mode indicate
common interface. The settings available for this register support
various combinations of edge and level detection in either originate
or
answer mode with ring indicator (RI) pulse enabled or disabled. To
see if
your modem supports MI/MIC and if it does, for particulars as to how
the
jack setting specified with the &J command interacts with this
register,
see your modem's user documentation.
------------------------------------------------------------------------
0 MI/MIC disabled
1 level triggered, originate mode, RI pulse
enabled
3 edge triggered, originate mode, RI pulse
enabled
5 level triggered, answer mode, RI pulse enabled
7 edge triggered, answer mode, RI pulse enabled
9 level triggered, originate mode, RI pulse
disabled
11 edge triggered, originate mode, RI pulse disabled
13 level triggered, answer mode, RI pulse disabled
15 edge triggered, answer mode, RI pulse disabled
------------------------------------------------------------------------
Note: This feature is not available to all modems. Refer to the feature
list in your modem's installation information. Setting S92 to a value
other than its factory-set default of 0 automatically redefines the
telephone line jack setting specified by the &J command.
S93 V.25bis DTE Interface Speed
S93 selects the speed used when the modem is configured for V.25bis
mode. When autobauding in any mode other than V.25bis, the modem uses
the value held in S37.
-----------------------------------------------------------------------
3 300 bps
5 1200 bps
6 2400 bps
7 4800 bps
8 7200 bps
9 9600 bps
10 12000 bps
11 14400 bps
12 19200 bps
13 38400 bps
------------------------------------------------------------------------
Note that the V.25bis feature is not available in all modems and if
supported, not all values may apply. Refer to the feature list in your
modem's user documentation.
S94 Mode Selection Register
S94 provides an alternative to setting internal DIP switches when
choosing between the AT command mode (factory setting) and the various
CCITT V.25bis command modes supported by the modem. To use this
register, the related DIP switches in the modem must be set to select
the "AT Command Mode" (factory setting). See your modem's installation
information.
With the modem's DIP switches set to select "AT Command Mode," the
operating mode after a soft reset is determined by S94. This register
is
read from nonvolatile memory at power-on; the &W command saves
the
current setting of this register in nonvolatile memory. Here are the
values for S94:
Synchronous Operation
Value Sync/ AT/
Addressed/ HDLC/BSC ASCII/EBCDIC
------------------------------------------------------------------------
Async V.25bis
Direct
0 Async AT
--
-- --
1 Async V.25bis
Addressed --
--
2 Sync V.25bis
Addressed HDLC
ASCII
3 Sync V.25bis
Addressed BSC
ASCII
4 Async AT
--
-- --
5 Async V.25bis
Direct --
--
6 Sync V.25bis
Direct HDLC
ASCII
7 Sync V.25bis
Direct BSC
ASCII
8 Async AT
--
-- --
9 Async V.25bis
Addressed --
--
10 Sync V.25bis
Addressed HDLC
EBCDIC
11 Sync V.25bis
Addressed BSC
EBCDIC
12 Async AT
--
-- --
13 Async V.25bis
Direct --
--
14 Sync V.25bis
Direct HDLC
EBCDIC
15 Sync V.25bis
Direct BSC
EBCDIC
------------------------------------------------------------------------
An alternative way of presenting the V.25bis mode selection options
listed above follows:
Value Mode
------------------------------------------------------------------------
0 Standard AT command
operation (factory setting)
1 Asynchronous V.25bis
using addressed access
2 Synchronous V.25bis
(HDLC framing) using addressed access
3 Synchronous V.25bis
(BSC framing) using addressed access
+4 Direct access calling
procedure
+8 EBCDIC character set options
instead of ASCII
------------------------------------------------------------------------
S95 Negotiation Message Options
S95 enables various result codes that indicate the sequence of events
in
the establishment of an error-control connection. This register does
not
affect the way in which the modem negotiates the connection; it merely
enables message options. The factory setting for this register is value
0, no bits selected. To enable any combination of the bits, add the
value(s) to the right of the bit number and set the register to this
sum.
Note: The bit values of S95 may be set to override some of the
characteristics of the Wn command. Setting any of the S95 bits to "1"
enables the corresponding result codes regardless of the Wn command
in
effect. Changing the Wn command setting does not affect the value set
for this register.
Bit Value Explanation
------------------------------------------------------------------------
0 1
Verbose CONNECT result code indicates the DCE speed
(rather than DTE speed). Numeric result codes are also
different when CONNECT reports DCE speed.
1 2
Append "/ARQ" to CONNECT result code when an
error-control connection is made.
2 4
Add CARRIER messages
3 8
Add PROTOCOL messages
4 16 Add
AUTOSTREAM messages
5 32 Add
COMPRESSION messages
------------------------------------------------------------------------
For example, if you want to add the compression result code (with W1
selected), you would select bit 5 (value of 32). The command line
ATS95=32J<CR> will then enable the COMPRESSION negotiation messages.
Refer to the Wn and Xn commands for additional and related information.
S97 V.32 Automode V.22/V.22bis Probe Timing
S97 sets the duration of the signal used by the modem in the answer
mode
during a V.32 automode handshake to determine if the calling modem
is of
V.22 or V.22bis type. The value of S97 also sets the time during which
the modem will reject the V.22/V.22bis probe signal when executing
the
V.32 automode handshake in the originate mode. The range of S97 values
is 15 to 70, representing 1.5 to 7.0 seconds. The default value of
30
(3.0 seconds) provides the timing necessary to connect to most V.22bis
compatible modems. When compatibility with V.32 "late connecting modems"
is a primary requirement, S97 should be set to 15. This value is also
compatible with the timing specified in CCITT recommendation V.22bis.
S105 Link Layer (N401/V.42 or N1/X.25) Frame Size Selector;
S105 sets the maximum frame size (N401 in V.42, N1 in X.25) according
to
the following parameter value-to-frame size (in bytes) conversions:
Value Explanation
------------------------------------------------------------------------
4 16 bytes
5 32 bytes
6 64 bytes
7 128 bytes (default)
8 256 bytes
9 512 bytes
------------------------------------------------------------------------
S108 Signal Quality Selector;
S108 sets the signal quality required for the modem handshake at the
highest designated V.32bis speed and for automatic rate re-negotiation.
If the modem determines during a carrier handshake or connection that
the signal quality is less than that specified by the value assigned
to
S108, the modem will attempt to connect at the next lower carrier speed
specified by S109 - unless the N0 command has been selected. If the
N0
command has been selected, then only the carrier speed specified by
S37
is used. This register only affects V.32bis connections. (Refer to
the
discussion of rate re-negotiation in the description of register S110
for related information.)
Value Explanation
------------------------------------------------------------------------
0 No limit.
1 Low quality.
2 Medium quality.
3 High quality.
------------------------------------------------------------------------
S109 V.32bis Carrier Speed Selector
S109 controls the speeds available for V.32bis carrier handshake,
retrains, and rate re-negotiation. This permits disabling speeds
lower
than the highest carrier speed while enabling the highest carrier speed
or other carrier speeds. (Refer to the discussion of rate re-negotiation
in the description of register S110 for related information.)
S37 selects the highest carrier speed. If the N0 command is selected,
the carrier speed specified by S37 and one of the carrier speeds
specified by S109 must match; the modem will connect only at that
carrier speed. While the modem is in V.32bis mode, the S37 and N0
command settings do not affect the modem speed during retrain or rate
re-negotiation procedures.
Caution: If speed negotiation is disabled by the N0 command and S37
indicates a V.32bis speed that is not enabled by S109, then the modem
will not connect. N0 and S37 have no effect during retrains and rate
re-
registration.
Decimal Explanation
Value
-------------------------------------------------------------------------
1 reserved
2 4800 bps
4 7200 bps
8 9600 bps
16 12000 bps
32 14400 bps
64 reserved
128 reserved
------------------------------------------------------------------------
Note: The decimal values may be added to specify several speeds from
which the modem can choose. For example, the factory default is 62
which
is the addition of decimal values 2, 4, 8, 16, and 32 (2+4+8+16+32=62).
S110 V.32/V.32bis Selector
The V.32 and V.32bis carrier handshake procedures are compatible. The
rate sequence (defined in V.32 and V.32bis) contains bit combinations
that specify which procedure shall be used. S110 provides control of
that selection for users who want to disable automatic rate re-
negotiation or limit the carrier handshake procedure to that specified
by V.32. (Refer to the description of registers S108 and S109 for
related information.)
When the value of S110 is 0, the V.32 handshake procedure follows. This
means that rate re-negotiation, which is allowed by V.32bis, is
disabled, and the &U command determines whether or not Trellis
coding is
enabled.
When the value of S110 is 1, the V.32bis handshake is enabled, but
automatic rate re-negotiation (defined on the next page) is disabled.
The modem shall respond to a rate re-negotiation request from the other
end.
When the value of S110 is 2 (factory-setting), V.32bis handshake and
automatic rate re-negotiation are enabled.
Value Explanation
------------------------------------------------------------------------
0 V.32 enabled.
1 V.32bis enabled.
2 V.32bis and automatic rate re-negotiation
enabled.
------------------------------------------------------------------------
Retrain and rate re-negotiation may be initiated, as follows, by either
modem involved in a V.32bis connection.
Rate Re-Negotiation:
Rate re-negotiation may be initiated by the other end modem, manually
by
the O3 command (while in the on-line command state), and by the modem
when the signal quality or frame error rate indicate a lower or higher
speed should be used.
When in the V.32bis mode, the modem always responds to a rate re-
negotiation request from the other modem. The speeds to be indicated
to
the other modem correspond to the speeds allowed by S109.
Automatic Rate Re-negotiation:
Retrains and rate re-negotiation initiated by the modem are called
"automatic" retrains or rate re-negotiations, respectively. Automatic
rate re-negotiation is always disabled when:
*the &X1 command is selected and the modem
is in the synchronous
mode (&Q1, &Q2, or &Q3 selected) or
*the modem is in asynchronous mode (&Q0
selected).
When the modem recognizes that signal quality has dropped, the modem
may
(if enabled by the &B1 command or the value of S110) initiate a
retrain
or rate re-negotiation. The procedure is to try a retrain first. If
that
does not yield acceptable signal quality or frame error rate, the modem
will try to re-negotiate a lower speed.
Line speed changes are only allowed when the modem is using a constant
DTE speed and in synchronous mode when the modem controls the DTE speed.
That is, rate re-negotiation speed changes are allowed only when the
&Q4, &Q5, or &Q6 command is selected and when the &X0
or &X2 commands
and one of the synchronous mode commands (&Q1, &Q2, or &Q3)
are
selected.
AutoSync Mode:
Increases in line speed are allowed when AutoSync is in use only to
the
extent that the current DTE speed will support AutoSync. The following
DTE speeds are required for the indicated line speeds, and are
established when the initial connection is made. If the line speed
is
reduced from the initial line speed of a call, then the DTE speed will
always support a return to the initial line speed. The following table
shows the maximum line speeds (in bps) that will be supported by initial
AutoSync DTE speeds.
Maximum AutoSync Line Speeds
Initial line speed DTE speed
Maximum line speed
------------------------------------------------------------------------
4800
9600 4800
7200
19200 12000
9600
19200 12000
12000
34400 14400
14400
34400 14400
------------------------------------------------------------------------
Error-control Mode:
When error correction is provided by the modem, automatic rate re-
negotiation, if enabled, is based on the current frame error rate.
Non Error-control Mode:
Automatic rate re-negotiation is based on signal quality when the modem
is using a constant DTE speed and not providing error correction and
when the modem is operating in synchronous mode. That is, 1) when the
&Q6 command is selected, or 2) &Q4 is selected and BSC mode
is in use,
or 3) the &X0 command is selected and the modem is in &Q1,
&Q2, or &Q3
mode.
Rate changes may be attempted according to the following:
*If the signal quality falls below the limit
set by S108, first try
a retrain. If the signal quality stays below the limit, attempt the
next
lower speed if that speed is allowed by S109.
*Never attempt to increase the line speed.
Note: Sometimes a rate re-negotiation attempt will not produce a
different speed because the speeds which the distant modem has enabled
match the local modem speeds only at the current speed.
DTE Interface Leads:
Depending on the settings of &Q, and &R, interface leads CTS
(circuit
106) and RD (circuit 104) may be clamped when a retrain or rate re-
negotiation process starts, and released when the process is completed.
S115 V.25bis Auto-answer and Character
Format Options
S115 is a bit-mapped register that specifies which auto-answer and
character format methods the modem will use during V.25bis operation.
The
range of values for this register is 0-3, with a factory setting of
0.
Value
Explanation
-----------------------------------------------------------------------
0
Use &E1 parity and V.25bis auto-answer.
1
Use 7E1 parity and alternate auto-answer method.
2
Use 8N1 parity and V.25bis auto-answer.
3
Use 8N1 parity and alternate auto-answer method.
-----------------------------------------------------------------------
The bit values for S115 specify the following:
Bit Value Definition
-----------------------------------------------------------------------
bit 0=0
Specifies V.25bis auto-answer, which does the following:
* Auto-answer after two rings unless a DIC (disregard
incoming call) is received for the DTE before the second
ring of a pending call*.
* Answer if a CIC (connect incoming call) is received
during a pending call.
* Inhibit auto-answer if DIC is received during the
currebt pending call.
* Issue an INV (invalid command) result code if a DIC or
CIC is received between pending calls.
bit0=1
Specifies an alternate auto-answer method, which does
the following:
* Auto-answer as specific by the S0 register.
* Answer if a CIC is received while an incoming call is
pending (regardless of the S0 setting).
* Inhibit auto-answer if a DIC is received during the
pending call.
* Issue an INV result code if a DIC or a CIC is received
between pending calls.
bit 1=0
Specifies 7 data bits, even parity, and one stop bit.
bit1=1
Specifies 8 data bits, no parity, and one stop bit.
-----------------------------------------------------------------------
Note: The term "pending call" means the period of time when an incoming
call attempt is active, which is indicated when S1 contains a non-zero
value and which is true from the first ring until 8 seconds of no ringing
has been detected.
S120 Auto Answer Control through DTR
S120 controls how DTR is used during auto answer. The range for S20
is 0
to 2, with a factory-set default of 0 (zero).
Value Explanation
-----------------------------------------------------------------------
0 If &D2
with &Q2 (or &Q4) is in effect, then DTR must be high
in order to permit S0 to enable auto-answer.
1 DTR is
not required to enable auto-answer.
2 DTR must
be on in order to enbable auto-answer.
-----------------------------------------------------------------------