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SLIMP—Limp Mode
1 = A loss of input signal reference has been detected, and the VCO is running at
approximately one-half the maximum speed (affected by the X-bit ), determined
from an internal voltage reference.
0 = External input signal frequency is at VCO reference.
SLOCK—Synthesizer Lock
1 = VCO has locked onto the desired frequency (or system clock is driven
externally).
0 = VCO is enabled, but has not yet locked.
RSTEN—Reset Enable
1 = Loss of input signal causes a system reset.
0 = Loss of input signal causes the VCO to operate at a nominal speed without
external reference (limp mode), and the device continues to operate at that
speed.
STSIM—Stop Mode System Integration Clock
1 = When LPSTOP is executed, the SIM40 clock is driven from the VCO.
0 = When LPSTOP is executed, the SIM40 clock is driven from an external crystal or
oscillator, and the VCO is turned off to conserve power.
STEXT—Stop Mode External Clock
1 = When the LPSTOP instruction is executed, the external clock pin (CLKOUT) is
driven from the SIM40 clock as determined by the STSIM bit.
0 = When the LPSTOP instruction is executed, the external clock (CLKOUT) is held
low to conserve power. No external clock will be driven in LPSTOP mode.
4.3.4 Chip Select Registers
The following paragraphs provide descriptions of the registers in the chip select function,
and an example of how to program the registers. The chip select registers cannot be used
until the V-bit in the MBAR is set.
MOTOROLA
MC68340 USER’S MANUAL
4- 29
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