Motorola MC68824 User Manual page 72

2. The TBC encodes the command found in CR on TXSYM1 and TXSYM2 with TXSYMO= 1
and SMREO equal to zero.
3. The TBC waits indefinitely for ACK or NACK coding on RXSYM1 and RXSYM2 as well as
SMIND=O from the modem.
NOTES
The modem is free to go to idle before transitioning to this state. If the modem does
not respond after a reasonable length of time, a software or hardware RESET must be
issued to the TBC.
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4. The TBC samples the ACKINACK signals (RXSYM1 and RXSYM2) and issues idle to the
modem (TXSYM2=0, TXSYM1 =0, while TXSYMO=1, and SMREO=O).
5. The TBC waits for the modem to respond with idle (RXSYM2=0, RXSYM1 =0, while
SMIND=O).
NOTE
If the modem does not respond after a reasonable length of time, a software or hardware
RESET must be issued to the TBC.
6. The TBC updates the CPA result with the ACKINACK and command done bits.
7. At this point, the TBC is in SM idle mode with TXSYM2=0, TXSYM1 =0, TXSYMO= 1, and
SMREO=O. The modem is in the idle state with RXSYM2=0, RXSYM1 =0, and SMIND=O.
S. The TBC is ready to accept another command.
3.8.1.2 DATA TRANSFER COMMANDS. Data transfer commands are designed for intelligent mo-
dems which need more information. The serial station management data interface provides a
sophisticated way for the host to communicate with the modem through the TBC. Upon receiving
this type of command the TBC will go through the steps described below:
1. It is assumed that the TBC and the modem are in MAC mode or that a modem error just
occurred.
2. The TBC issues the data transfer command found in CR with TXSYMO=1 and SMREO=O
to the mO,dem.
3. The TBC waits indefinitely for the modem to assert SMIND = O.
NOTE
If the modem does not respond after a reasonable length of time, a software or hardware
RESET must be issued to the TBC.
4. The TBC samples RXSYM 1 and RXSYM2 for ACKINACK from now to the end of the received
data stream.
5. The TBC outputs the bit stream taken from CPA VALO (16 bits from 0 to 15) on TXSYMO.
The data word in CPA VALO must include the start bit as shown to conform to S02.4G:
CPA VALO: D C B A 4
Data
Start Bit
NOTE
The programmer does not have to furnish the stop bit.
To conform to S02.4G only one data byte may be sent at a time. If more than one data
byte needs to be sent, then more data commands must be given.
MC68824 USER'S MANUAL MOTOROLA
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