Serial Management Controllers (SMCs)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
29-8
Freescale Semiconductor
29.2.4
Disabling SMCs On the Fly
An SMC can be disabled and reenabled later by ensuring that buffers are closed properly and new data is
transferred to or from a new buffer. Such a sequence is required if the parameters to be changed are not
dynamic. If the register or bit description states that on-the-fly changes are allowed, the sequences need
not be followed and the register or bits may be changed directly.
Note that the SMC does not have to be fully disabled for parameter RAM to be modified.
Table 29-2
describes when parameter RAM values can be modified. To disable the SCCs, SMCs, SPI, and the I
2
C,
use CPCR[RST] to reset the CPM.
29.2.4.1
SMC Transmitter Full Sequence
Follow these steps to fully enable or disable the SMC transmitter:
1. If the SMC is sending data, issue a
STOP
TRANSMIT
command to stop transmission smoothly. If the
SMC is not sending, this command is not required.
2. Clear SMCMR[TEN] to disable the SMC transmitter and put it in reset state.
3. Update SMC transmit parameters, including the parameter RAM. To switch protocols or
reinitialize parameters, issue an
INIT
TX
PARAMETERS
command.
4. Issue a
RESTART
TRANSMIT
if an
INIT
TX
PARAMETERS
was not issued in step 3.
5. Set SMCMR[TEN]. Transmission now begins using the TxBD that the TBPTR value points to as
soon as the R bit is set in that TxBD.
29.2.4.2
SMC Transmitter Shortcut Sequence
This shorter sequence reinitializes transmit parameters to the state they had after reset.
1. Clear SMCMR[TEN].
2. Make any changes, then issue an
INIT
TX
PARAMETERS
command.
3. Set SMCMR[TEN].
29.2.4.3
SMC Receiver Full Sequence
Follow these steps to fully enable or disable the receiver:
1. Clear SMCMR[REN]. Reception is aborted immediately, which disables the SMC receiver and
puts it in a reset state.
2. Modify SMC receive parameters, including parameter RAM. To switch protocols or reinitialize
SMC receive parameters, issue an
INIT
RX
PARAMETERS
command.
3. Issue a
CLOSE
RXBD
command if
INIT
RX
PARAMETERS
was not issued in step 2.
4. Set SMCMR[REN]. Reception immediately uses the RxBD that RBPTR points to if E is set in that
RxBD.
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Страница 1162: ...Fast Ethernet Controller FEC MPC885 PowerQUICC Family Reference Manual Rev 2 45 40 Freescale Semiconductor ...
Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
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Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
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Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
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