MC68F375
SINGLE-CHIP INTEGRATION MODULE 2 (SCIM2E)
MOTOROLA
REFERENCE MANUAL
Rev. 25 June 03
4-3
The SCIMMCR register controls the system configuration. SCIMMCR can be read or
written at any time, except for the module mapping (MM) bit, which can only be written
once after reset, and the reserved bit, which is read-only. Writes have no effect.
Table 4-1 SCIMMCR Bit Descriptions
Bit(s)
Name
Description
15
EXOFF
External clock off.
0 = The CLKOUT pin is driven during normal operation.
1 = The CLKOUT pin is placed in a high-impedance state.
14
FRZSW
Freeze software enable. Enables or disables the software watchdog and periodic interrupt timer
during background debug mode when FREEZE is asserted.
0 = Enables the software watchdog and periodic interrupt timer when FREEZE is asserted.
1 = Disables the software watchdog and periodic interrupt timer when FREEZE is asserted.
13
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.
12
CPUD
CPU development support disable. CPUD is cleared to zero when the MCU is in an expanded
mode, and set to one in single-chip mode.
0 = Instruction pipeline signals available on pins IPIPE and IFETCH.
1 = Pins IPIPE and IFETCH placed in high-impedance state unless a breakpoint occurs.
11
—
Reserved
10
SLOWE
Slow mode enable. Control bit which forces pins on the chip to operate in fast mode regardless
of how they are set up from the controlling module. Slow mode is enabled by setting this bit.
0 = Pins setup by the controlling module to operate in slow mode will operate in fast mode.
1 = Pins will operate at the normal speed controlled by the module.
9:8
SHEN
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 4- 3 indicates whether show cycle data is driven externally, and whether external bus arbitration
can occur. To prevent bus conflict, external devices must not be selected during show cycles.
7SUPV
Supervisor/user data space. The SUPV bit places the SCIM2E global registers in either super-
visor or user data space.
0 = Registers access controlled by the SUPV bit accessible in either supervisor or user mode.
1 = Registers access controlled by the SUPV bit restricted to supervisor access only.
6MM
Module mapping
0 = Internal modules are addressed from 0x7FF000 – 0x7FFFFF.
1 = Internal modules are addressed from 0xFFF000 – 0xFFFFFF.
5
ABD
Address Bus Disable. ABD is cleared to zero when the MCU is in an expanded mode, and set
to one in single-chip mode. ABD can be written only once after reset.
0 = Pins ADDR[2:0] operate normally.
1 = Pins ADDR[2:0] are disabled.
4RWD
Read/write disable. RWD is cleared to zero when the MCU is in an expanded mode, and set to
one in single-chip mode. RWD can be written only once after reset.
0 = R/W signal operates normally
1 = R/W signal placed in high-impedance state.
3:0
IARB
Each module that can generate interrupts, including the SCIM2E, has an IARB field. Each IARB
field can be assigned a value from 0x0 to 0xF. During an interrupt acknowledge cycle, IARB per-
mits arbitration among simultaneous interrupts of the same priority level. The reset value of the
SCIM2 IARB field is 0xF, the highest priority. This prevents SCIM2 interrupts from being discard-
ed during system initialization.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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