- Multi-Tech Modem User Guide

97
Appendix D - V.25bis Operation
Another asynchronous mode concern is the problem of connecting at a different speed than the
speed at which the serial port is set. If your modem port speed is different from the serial port speed,
you must either:
1) Enable speed conversion and have flow control on, or
2) Enable connect responses (with the
ATX1 command) and change the serial baud rate
after receiving a connect message.
If the
$VD1 command is entered when in Auto-Answer mode, the modem answers immediately upon
receiving the first ring.
There is no disconnect message ( NO CARRIER ) if a normal connection is made.
V.25bis Set-Up and Initialization
Before you operate your modem in the V.25 bis mode, you need to make sure it is set up properly
(various RS-232 lines such as DSR and CTS act as specified in the V.25 bis standard). Setup
involves proper DIP-Switch settings and soft-switches (software controlled conditions).
V.25bis DIP-Switches
#1 Unforced DTR
#2 NA
#3 NA
#4 NA
#5 Auto-Answer enabled
#6 Async - Max throughput set
Sync - Slave Clocking unforced
#8 Command Mode forced
#9 Digital Loopback Off
#10 Dial-Up
#11 Async - AT/Multi-Tech Resp.
#12 Async/Sync mode set per requirements
V.25bis Mode AT Commands
The following commands will either alter standard V.25 bis behavior (so you must be careful in their
use) or they are not allowed, as indicated. All other commands can be used in V.25 bis operation.
A Not Allowed
A/ Not Allowed
A: Not Allowed
D Not Allowed
D...N Not Allowed
$D Alters Operation ($D1 in V25 bis is direct call mode)
E Alters Operation
&F Alters Operation (removes modem from asynchronous V.42 bis mode)
N Not Allowed
N...N Not Allowed
O Not Allowed
P Not Allowed
T Not Allowed
U Not Allowed
W Not Allowed
X Alters Operation (X0 no connect message, X1 connect message)
, Not Allowed
; Not Allowed
! Not Allowed
@ Not Allowed
+++AT<CR> Not Allowed