Datasheet

MC68331TS/D 17

Figure 6 System Configuration and Protection Block

3.2.1 System Configuration

The SIM controls MCU configuration during normal operation and during internal testing.

The SIM configuration register controls system configuration. It can be read or written at any time, ex-

cept for the module mapping (MM) bit, which can be written only once.

EXOFF —External Clock Off

0 = The CLKOUT pin is driven from an internal clock source.

1 = The CLKOUT pin is placed in a high-impedance state.

FRZSW —Freeze Software Enable

0 = When FREEZE is asserted, the software watchdog and periodic interrupt timer counters con-

tinue to run.

1 = When FREEZE is asserted, the software watchdog and periodic interrupt timer counters are dis-

abled, preventing interrupts during software debug.

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.

SIMCR

—SIM Configuration Register

$YFFA00

14 13 12 11 10 9 8 7 6 5 4 3 0

EXOFF FRZSW FRZBM 0 SLVEN 0 SHEN SUPV MM 0 0 IARB

RESET:

0 0 0 0 DATA11 0 0 0 1 1 0 0 1 1 1 1

300 SYS PROTECT BLOCK

RESET STATUS

HALT MONITOR

BUS MONITOR

SPURIOUS INTERRUPT MONITOR

SOFTWARE WATCHDOG TIMER

PERIODIC INTERRUPT TIMER

PRESCALER

CLOCK

IRQ[7:1]

BERR

RESET REQUEST

Freescale Semiconductor, I

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com