RCVDL56DPFL/SP, RCV56DPFL/SP, and RCV336DPFL/SP Designer’s Guide
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6.6 RETRAIN AND AUTOMATIC RATE CHANGE
This section explains how to perform the retrain and rate change.
6.6.1 Retrain Without a Rate Change
K56flex/V.34/V.32/V.32 bis and V.22 bis Configurations
When the RTRN bit is set to a 1, the MDP will initiate the retrain sequence. The modem which detects the retrain sequence
will respond with training, and both modems will proceed with the proper training sequence. The retrain process can be
monitored by observing the appropriate status bits in the transmitter and receiver.
6.6.2 Retrain With a Rate Change
K56flex/V.34/V.32/V.32 bis and V.22 bis Configurations
The following procedure describes how to obtain a rate change along with a retrain.
1. Store the desired configuration in the CONF register. Use configuration code 82h (V.22 bis/1200) for fall forward or
fallback between 2400 bps and 1200 bps. NOTE: Do not set the NEWC bit.
2. Set the RTRN bit to a 1.
The MDP will then send the retrain sequence at the correct operating speed as selected in the configuration registers. The
rate sequence is automatically changed in the training sequence to tell the other modem at what speed to operate. The
status bits will change as mentioned above and the CTS bit will be set to a 1 when the retrain sequence is completed. (See
the RREN bit description in Table 3-1 for rate change procedures in K56flex/V.34/V.32 bis modes using a rate renegotiation
rather than a retrain. Also, see the SRCEN bit description in Table 3-1 for rate change procedures in V.34 mode using the
secondary channel.)
6.7 HANDSHAKE TIME-OUT TIMERS
If any part of the handshake is not detected, the MDP will time out and abort the handshake. In this case, the transmitter will
immediately stop sending the training sequence. Also, the MDP, upon timing out, will load an error code into register 14
(ABCODE) of interface memory that indicates that point in the handshake the time-out occurred. The error code is not
cleared even if the MDP immediately goes into a new handshake after aborting. The user can observe this register during
the handshake to determine if an abort occurred.
The user can progressively observe the handshake detector bits (AADET, ACDET, CCDET, SECTXD, SECRXD, etc.) to
determine how the handshake is proceeding. The user can thus be interrupted at each step of the handshake progression.
The K56flex, V.34, and V.32 handshake error codes and their meanings are:
Error Code
Reason For Aborting (Time-out)
00
No error
01- FF
See ABCODE in Table 3-1 and error code
definitions in Table 3-2.
Summary of Contents for RC336DPFL
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