MPC555
/
MPC556
MODULAR INPUT/OUTPUT SUBSYSTEM (MIOS1)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
15-41
15.15.3 MIOS1 Double Edge Single Output Pulse Generation
Software can initialize the MIOS1 to generate both the rising and the falling edge of an
output pulse. With a MDASM, pulses as narrow as 50 ns can be generated since soft-
ware action is not needed between the edges. Pulses as long as 2.1 s can be gener-
ated. When an interrupt is desired, it can be selected to occur on every edge or only
after the second edge.
shows how a counter submodule and a MDASM can be used to gener-
ate 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 MDASM automatically creates
both edges and the pulse can be selected by software to be a high-going or a low-go-
ing. After the trailing edge, the MDASM stops to await further commands from the soft-
ware. Note that a single edge output can be generated by writing to only one register.
Figure 15-11 MIOS1 Example: Double Edge Output Compare
16-bit Up-Counter
Submodule Bus
Clock
Select
16-bit Compare B
Output
Flip-Flop
Output
Pin
16-bit Compare A
16-bit Register B2
16-bit Register A
Output
Compare
Interrupt
on
From
Prescaler
or Pin
Trailing
Bus
Select
Edge
Two
16-bit
Counter
Buses
MIOS Double Action Submodule
in OCB mode (MOD3 - MOD0 = 0b0100)
MIOS Modulus Counter Submodule
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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