
MC68336/376
REGISTER SUMMARY
MOTOROLA
USER’S MANUAL
D-7
FRZSW — Freeze Software Enable
0 = When FREEZE is asserted, the software watchdog and periodic interrupt timer
counters continue to run.
1 = When FREEZE is asserted, the software watchdog and periodic interrupt timer
counters are disabled, preventing interrupts during background debug mode.
FRZBM — Freeze Bus Monitor Enable
0 = When FREEZE is asserted, the bus monitor continues to operate.
1 = When FREEZE is asserted, the bus monitor is disabled.
SHEN[1:0] — Show Cycle Enable
The SHEN field determines how the external bus is driven during internal transfer
operations. A show cycle allows internal transfers to be monitored externally.
Table D-4 shows whether show cycle data is driven externally, and whether external
bus arbitration can occur. To prevent bus conflict, external peripherals must not be en-
abled during show cycles.
SUPV — Supervisor/Unrestricted Data Space
The SUPV bit places the SIM global registers in either supervisor or user data space.
0 = Registers with access controlled by the SUPV bit are accessible in either
supervisor or user mode.
1 = Registers with access controlled by the SUPV bit are restricted to supervisor
access only.
MM — Module Mapping
0 = Internal modules are addressed from $7FF000 – $7FFFFF.
1 = Internal modules are addressed from $FFF000 – $FFFFFF.
IARB[3:0] — Interrupt Arbitration ID
Each module that can generate interrupts, including the SIM, has an IARB field. Each
IARB field can be assigned a value from $0 to $F. During an interrupt acknowledge
cycle, IARB permits arbitration among simultaneous interrupts of the same priority lev-
el. The reset value of the SIM IARB field is $F. This prevents SIM interrupts from being
discarded during system initialization.
D.2.2 System Integration Test Register
SIMTR — System Integration Test Register
$YFFA02
Used for factory test only.
Table D-4 Show Cycle Enable Bits
SHEN[1:0]
Action
00
Show cycles disabled, external arbitration enabled
01
Show cycles enabled, external arbitration disabled
10
Show cycles enabled, external arbitration enabled
11
Show cycles enabled, external arbitration enabled;
internal activity is halted by a bus grant
336376UMBook Page 7 Friday, November 15, 1996 2:09 PM