MPC555
/
MPC556
QUEUED SERIAL MULTI-CHANNEL MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
14-5
14.5.1 Low-Power Stop Operation
When the STOP bit in QSMCMMCR is set, the IMB clock input to the QSMCM is dis-
abled and the module enters a low-power operating state. QSMCMMCR is the only
register guaranteed to be readable while STOP is asserted. The QSPI RAM is not
readable in low-power stop mode. However, writes to RAM or any register are guar-
anteed valid while STOP is asserted. STOP can be written by the CPU and is cleared
by reset.
System software must bring each submodule to an orderly stop before setting STOP
to avoid data corruption. The SCI receiver and transmitter should be disabled after
transfers in progress are complete. The QSPI can be halted by setting the HALT bit in
SPCR3 and then setting STOP after the HALTA flag is set.
14.5.2 Freeze Operation
The FRZ1 bit in QSMCMMCR determines how the QSMCM responds when the IMB3
FREEZE signal is asserted. FREEZE is asserted when the CPU enters background
debug mode. Setting FRZ1 causes the QSPI to halt on the first transfer boundary fol-
lowing FREEZE assertion. FREEZE causes the SCI1 transmit queue to halt on the first
transfer boundary following FREEZE assertion.
14.5.3 Access Protection
The SUPV bit in the QMCR defines the assignable QSMCM registers as either super-
visor-only data space or unrestricted data space.
When the SUPV bit is set, all registers in the QSMCM are placed in supervisor-only
space. For any access from within user mode, the IMB3 address acknowledge (AACK)
signal is asserted and a bus error is generated.
Because the QSMCM contains a mix of supervisor and user registers, AACK is assert-
ed for either supervisor or user mode accesses, and the bus cycle remains internal. If
a supervisor-only register is accessed in user mode, the module responds as if an ac-
cess had been made to an unauthorized register location, and a bus error is generat-
ed.
Table 14-2 QSMCM Global Registers
Access
1
NOTES:
1. S = Supervisor access only
S/U = Supervisor access only or unrestricted user access (assignable data space).
Address
MSB
2
2. 8-bit registers reside on 8-bit boundaries. 16-bit registers reside on 16-bit boundaries.
LSB
S
0x30 5000
QSMCM Module Configuration Register (QSMCMMCR)
See
T
0x30 5002
QSMCM Test Register (QTEST)
S
0x30 5004
Dual SCI Interrupt Level (QDSCI_IL)
See
for bit descriptions.
Reserved
S
0x30 5006
Reserved
Queued SPI Interrupt Level (QSPI_IL)
for bit descriptions.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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