Motorola MC68824 User Manual page 71

II
TXSYM2
1 TXSYM2 line to the modem is set to one while SMREO equals zero
o
TXSYM2 line to the modem is set to zero while SMREO equals zero
TXSYM1
1 TXSYM1 line to the modem is set to one while SMREO equals zero
o
TXSYM1 line to the modem is set to zero while SMREO equals zero
DATA
1 Perform data exchange with the modem
o
No data exchange
Note that the PHYSICAL command should not be given with a code of AO as this commands the
modem to enter the idle state without a data transfer. This action would then cause the modem
to respond with idle whereas the TBC would be waiting for ACK or NACK. Only the TBC is permitted
to issue idle to the modem without a data transfer.
The status word format returned in CPA RESULT is shown below:
x x x
RXACK - RXSYM1 Acknowledgement
1 Acknowledgement received
o
No acknowledgement received
RXNA - RXSYM2 Non-Acknowledgement
1 Non-acknowledged received
o
No non-acknowledgement received
COMCON - Command Configuration
1 Command confirmed
o
Command not confirmed
x -
Don't Care
x x
RXACK RXNA
I
COMCON
There are two main types of commands which can be issued by the host to the physical layer:
immediate and data transfer. Immediate commands do not involve data exchange with the modem
but rather provide a simple interface to allow the host to control the modem through the TBC.
Data transfer commands are designed for intelligent modems which need additional information
to be transferred between the host and the modem through the TBC.
3.S.1.1 IMMEDIATE COMMANDS. The immediate commands include reset, disable loopback,and
enable transmitter. Refer to 5.9. ;.4 TXSYM2, TXSYM1, AND TXYSMO IN STATION MANAGEMENT
MODE for a description of the encodings of these commands on the physical interface. The
following paragraphs describe the handshake between the TBC and the modem. The host loads
the command into the command register and the TBC passes the command to the modem by
encoding it on pins TXSYM1 and TXSYM2 while TXSYMO is set to one. Note that for immediate
commands, bit 2 (DATA) of the command register must be set to zero. 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.
MOTOROLA
MC68824 USER'S MANUAL
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