
MC68F375
CONFIGURABLE TIMER MODULE (CTM9)
MOTOROLA
REFERENCE MANUAL
Rev. 25 June 03
13-59
value when the output is to change. The software thus writes the compare value into
register A. In the SASM control register, the software establishes whether the output
flip-flop is to toggle to the opposite state, or is to go to a high or a low level. The output
compare interrupt is typically used to notify the software that the previous compare is
complete and the SASM is available for a new compare value in register A.
Figure 13-18 CTM9 Example — Single Edge Output Compare
13.11.5 CTM9 Double Edge Single Output Pulse Generation
Software can initialize the CTM9 to generate both the rising and the falling edge of an
output pulse. With a DASM, pulses as narrow as 0.119 microseconds can be gener-
ated since software action is not needed between the edges. Pulses as long as 3
seconds can be generated. When an interrupt is desired, it can be selected to occur
on every edge or only after the second edge.
Figure 13-19 shows how a counter submodule and a DASM can be used to generate
both edges of a single output pulse. The software puts the compare value for one edge
in register A and the other one in register B2. The DASM automatically creates both
edges, and the pulse can be selected by software to be a high-going or a low-going.
After the trailing edge, the DASM stops to await further commands from the software.
Note that a single edge output can be generated by writing to only one register.
16-Bit Up Counter
Two
Submodule Bus
16-Bit Compare
Output
Flip-Flop
Output
Pin
16-Bit Register A
Output
Compare
Single Action Submodule Channel
Interrupt
Bus
From
Prescaler
or Pin
16-Bit
Time-
Modulus Register
Modulus
Control
Clock
Select
Load
Base
Buses
Select
Bus
Select
Modulus Counter Submodule
Free-Running or
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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