Serial Communication Controllers (SCCs)
7-140
MC68360 USER’S MANUAL
MOTOROLA
states that dynamic changes are allowed, the following sequences are not required, and the
register or bit may be changed immediately. In all other cases, the sequence should be
used. For instance, the internal baud rate generators allow on-the-fly changes, but the
DPLL-related bits in the GSMR do not.
NOTE
The modification of parameter RAM does not require a full dis-
abling of the SCC. See the parameter RAM description for de-
tails on when parameter RAM values may be modified.
If the user desires to disable all SCCs, SMCs, and the SPI, then
the CR may be used to reset the entire CP with a single com-
mand.
7.10.14.1 SCC TRANSMITTER FULL SEQUENCE.
For the SCC transmitter, the full dis-
able and enable sequence is as follows:
1. STOP TRANSMIT command. This command is recommended if the SCC is currently
in the process of transmitting data since it stops transmission in an orderly way. If the
SCC is not transmitting (e.g., no Tx BDs are ready or the GRACEFUL STOP TRANS-
MIT command has been issued and has completed), then the STOP TRANSMIT com-
mand is not required. Furthermore, if the TBPTR will be overwritten by the user or the
INIT TX PARAMETERS command will be executed, this command is not required.
2. Clear the ENT bit in the GSMR, which disables the SCC transmitter and puts it in a
reset state.
3. Make modifications. The user may make modifications to the SCC transmit parame-
ters including the parameter RAM. If the user desires to switch protocols or restore the
SCC transmit parameters to their initial state, the INIT TX PARAMETERS command
may now be issued.
4. RESTART TRANSMIT command. This command is required if the INIT TX PARAME-
TERS command was not issued in step 3.
5. Set the ENT bit in the GSMR. Transmission will now begin using the Tx BD pointed to
by the TBPTR as soon as the Tx BD R-bit is set.
7.10.14.2 SCC TRANSMITTER SHORTCUT SEQUENCE.
A shorter sequence is possible
if the user desires to reinitialize the transmit parameters to the state they had after reset.
This sequence is as follows:
1. Clear the ENT bit in the GSMR.
2. INIT TX PARAMETERS command. Any additional modifications may now be made.
3. Set the ENT bit in the GSMR.
7.10.14.3 SCC RECEIVER FULL SEQUENCE.
The full disable and enable sequence for
the receiver is as follows:
1. Clear the ENR bit in the GSMR. Reception will be aborted immediately. This disables
the receiver of the SCC and puts it in a reset state.
2. Make modifications. The user may make modifications to the SCC receive parameters