S-register S202 for Rockwell modems

[Franc Zabkar]

I have an internal Dynalink controller-based ISA modem which uses the
Rockwell ACF2 chipset. Recently I came upon an S-register which
contains some interesting options.

The default setting for my modem is S202=0. This means that
potentially useful (?) features such as "V.90 digital pad
compensation" and "V.42 selective reject" are disabled.

By experimenting with various bit settings, I was able to confirm, via
post-call diagnostics, that my modem does occasionally negotiate an
"LAPM-SREJ" connection.

I can also confirm that setting bit 4 produces an AT&V2 diagnostic
string of the form "BEGIN...END" before every connect and disconnect
message. This may be useful when troubleshooting a connection using
HyperTerminal, or some other comms app.

Bit 2 causes a string of the form "RnnTnnRnnTnn..." to be output.
These numbers appear to correspond to the "Highest Rx/Tx State" data
in the AT&V1 report. An example follows:

R00T00R01T02T03R02T04T05R20T20T21R22R23T22R27T28R28R29R2AR2DR2BT29R24T24R25T25R2
CT2CR40T40R41R46R47R48T44T45T46T47R60T48R61R63T62T63T64R65T65T67R67

Bit 3 appears to disable AGC. I'm not sure where one would find this
useful.

I'm still experimenting with bit 6 (V.90 Tx level).

====================================================================
S202 - Bit Mapped Control Register

Controls K56flex/V90 Tx level and automatic &V2 status response.

Bit 0 K56Plus Protocol
0 = Follows the setting of ATNn.
1 = Forces LAPM when a K56Plus call is established.

Bit 1 Enable V.90 digital pad compensation.
0 = Disables V.90 digital pad compensation.
1 = Enables V.90 digital pad compensation.

Bit 2 Display Tx and Rx HNDSHK states

Bit 3 Reserved (used for Disable Auto-Gain on client modem)

Bit 4 Automatic &V2 status response
0 = No automatic &V2 status response
1 = Automatic &V2 status response before every connect message and
after every disconnect message

Bit 5 K56flex Tx level select
0 = -12 dBm
1 = - 6 dBm

Bit 6 V90 Tx level select
0 = -12 dBm
1 = - 6 dBm

Bit 7 Enable V.42 selective reject
0 = Disables V.42 selective reject.
1 = Enables V.42 selective reject
====================================================================

-- Franc Zabkar

Please remove one 'g' from my address when replying by email.