Motorola MC68824 User Manual page 73

II
6. The TBC waits indefinitely for the modem to assert the start bit i.e., RXSYMO = O.
NOTE
Ifthe modem does not respond after a reasonable length oftime, a software or hardware
RESET must be issued to the TBC. .
7. The TBC waits 16 clock cycles to sample the 16 bits after the start bit from RXSYMO.
S. The TBC asserts TXSYMO = 1, TXSYM 1 = 0, TXSYM2 = 0 with SMREQ = 0, thus issuing idle.
9. The TBC waits for the modem to respond with idle: RXSYM1 =0, RXSYM2=0, while
SMIND=O.
10. The TBC then copies the received word into CPA RET O. Bits 0 through 7 contain the data
returned by the modem while bits S through F contain all ones if the S02.4G interface was
used.
11. The TBC updates the CPA result with the ACKINACK and command done bits.
12. At this point, the TBC is in SM idle mode with TXSYM2=0, TXSYM1 =0, TXSYMO= 1, and
SMREQ=O. The modem is in the idle state with RXSYM2=0, RXSYM1 =0, and SMIND=O.
13. The TBC is ready to accept another command.
3.S.2 END PHYSICAL Command
This command causes the TBC to exit from station management mode. Upon receiving the
command, the TBC sets SMREQ=1, and waits for the modem to set SMIND=1 before setting
the command done bit (bit 0 of CPA RESULT). The coding for this command is AS and its format
is:
o
I
0
3.9 ILLEGAL COMMAND
Commands with bits 5, 6, and 7 set to zero are ILLEGAL commands to the TBC. A command with
this format will have no affect on the TBC and the command complete bit in the status word will
not be set. The format of an ILLEGAL command is shown below. The semaphore register will
contain 'FE' until the next command is passed by the host processor to the TBC.
x -
Don't Care
MOTOROLA
3-30
I
0
o
I
x
1 0
x
I
x
x
I
x
MC68824 USER'S MANUAL