MC68331CEH16 Datasheet, PDF (53/84 Pages) Freescale Semiconductor, Inc – 32-Bit Modular Microcontroller

Freescale Semiconductor, Inc.
5.3 QSM Registers
QSM registers are divided into four categories: QSM global registers, QSM pin control registers, QSPI
submodule registers, and SCI submodule registers. The QSPI and SCI registers are defined in separate
sections below. Writes to unimplemented register bits have no meaning or effect, and reads from unim-
plemented bits always return a logic zero value.
The module mapping bit of the SIM configuration register (SIMCR) defines the most significant bit
(ADDR23) of the address, shown in each register figure as Y (Y = $7 or $F). This bit, concatenated with
the rest of the address given, forms the absolute address of each register. Refer to the SIM section of
this technical summary for more information about how the state of MM affects the system.
5.3.1 Global Registers
The QSM global registers contain system parameters used by both the QSPI and the SCI submodules.
These registers contain the bits and fields used to configure the QSM.
QSMCR — QSM Configuration Register
$YFFC00
15
14
13
12
11
10
9
8
7
6
5
4
3
0
STOP FRZ1 FRZ0 0
0
0
0
0 SUPV 0
0
0
IARB
RESET:
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
The QSMCR contains parameters for the QSM/CPU/intermodule bus (IMB) interface.
STOP — Stop Enable
0 = Normal QSM clock operation
1 = QSM clock operation stopped
STOP places the QSM in a low-power state by disabling the system clock in most parts of the module.
The QSMCR is the only register guaranteed to be readable while STOP is asserted. The QSPI RAM is
not readable. However, writes to RAM or any register are guaranteed to be valid while STOP is assert-
ed. STOP can be negated by the CPU and by reset.
The system software must stop each submodule before asserting STOP to avoid complications at re-
start and to avoid data corruption. The SCI submodule receiver and transmitter should be disabled, and
the operation should be verified for completion before asserting STOP. The QSPI submodule should be
stopped by asserting the HALT bit in SPCR3 and by asserting STOP after the HALTA flag is set.
FRZ1 — Freeze 1
0 = Ignore the FREEZE signal on the IMB
1 = Halt the QSPI (on a transfer boundary)
FRZ1 determines what action is taken by the QSPI when the FREEZE signal of the IMB is asserted.
FREEZE is asserted whenever the CPU enters the background mode.
FRZ0 — Freeze 0
Reserved
Bits [12:8] — Not Implemented
SUPV — Supervisor/Unrestricted
0 = User access
1 = Supervisor access
SUPV defines the assignable QSM registers as either supervisor-only data space or unrestricted data
space.
IARB — Interrupt Arbitration Identification Number
The IARB field is used to arbitrate between simultaneous interrupt requests of the same priority. Each
module that can generate interrupt requests must be assigned a unique, non-zero IARB field value. Re-
fer to 3.8 Interrupts for more information.
MC68331TS/D
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