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System Integration Module (SIM60)
MC68360 USER’S MANUAL
NOTE
If the PIT is enabled with the PTP bit set, then the first interrupt
can be up to 512 clocks early.
6.9.3.8 SOFTWARE SERVICE REGISTER (SWSR). The SWSR is the location to which
the SWT servicing sequence is written. To prevent an SWT timeout, the user should write a
$55 followed by a $AA to this register. The SWT can be disabled by clearing the SWE bit in
the SYPCR. The SWSR can be written at any time, but returns all zeros when read.
SUPERVISOR ONLY
6.9.3.9 CLKO CONTROL REGISTER (CLKOCR). The CLKOCR controls the operation of
the CLKO2-1 pins. CLKOWP bit in CLKOCR is used as a protect mechanism to prevent
erroneous writing. CLKOCR can be read or written only in supervisor mode.
CLKOWP—CLKOCR Write Protect
This bit protects accidental writing into the CLKOCR. After reset, this bit defaults to zero
to enable writing. Setting this bit prevents further writing (excluding the first write that sets
this bit).
Bits 6 -4—Reserved
COM2—Clock Output 2 Mode
The COM2 bits control the output buffer strength of the CLKO2 pin. When both bits are
set, the CLKO2 pin is held in the high (1) state. These bits can be dynamically changed
without generating spikes on the CLKO2 pin. If the CLKO2 pin is not connected to external
circuits, set both bits (disabling the clock output) to minimize noise and power dissipation.
The COM2 bits are set to ones at system reset, unless MODCK = 01, in which case they
are cleared. This causes CLKO2 to be disabled at system reset, unless MODCK = 01.
(This causes CLKO2 to default to a quiet state, unless it is needed in an MC68040 com-
panion mode system.)
00 = Clock Out Enabled, Full-Strength Output Buffer
01 = Clock Out Enabled, 2/3-Strength Output Buffer
10 = Clock Out Enabled, 1/3-Strength Output Buffer
11 = Clock Out Disabled (Driving 1)
COM1—Clock Output 1 Mode
The COM1 bits control the output buffer strength of the CLKO1 pin. When both bits are
set, the CLKO1 pin is held in the high (1) state. These bits can be dynamically changed
76543210
SWSR7
SWSR6
SWSR5
SWSR4
SWSR3
SWSR2
SWSR1
SWSR0
76543210
CLKOWP
—
COM2
COM1
RESET:
0000
0/1
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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