Motorola MPC533 Reference Manual page 744

MIOS14 Modulus Counter Submodule (MMCSM)
17.8.1 MMCSM Features
• Programmable 16-bit modulus up-counter with a built-in programmable 8-bit
prescaler clocked by MCPSM
• Maximum increment frequency of the counter:
— clocked by the internal MCPSM output: f
— clocked by the external signal: f
• Flag setting and possible interrupt generation on overflow of the up-counter register
• Time counter on internal clock with interrupt capability after a pre-determined time
• External event counter (pulse accumulator) with overflow and interrupt capability
after a pre-determined number of external events
• Usable as a regular free-running up-counter
• Capable of driving a dedicated 16-bit counter bus to provide timing information to
action submodules (the value driven is the contents of the 16-bit up-counter register)
• Optional signal for counting external events
• Optional signal to externally force a load of the modulus counter
17.8.1.1 MMCSM Signal Functions
The MMCSM has two dedicated external signals.
An external modulus load signal (MMCnL) allows the modulus value stored in the modulus
latch register (MMCSMML) to be loaded into the up-counter register (MMCSMCNT) at
any time. Both rising and falling edges of the load signal may be used, according to the
EDGEP and EDGEN bit settings in the MMCSMSCR.
An external event clock signal (MMCnC) can be selected as the clock source for the
up-counter register (MMCSMCNT) by setting the appropriate value in the CLS bit field of
the status/control register (MMCSMSCR). Either rising or falling edge may be used
according to the setting of these bits.
When the external clock source is selected, the MMCSM is in the event counter mode. The
counter can simply counts the number of events occurring on the input signal. Alternatively,
the MMCSM can be programmed to generate an interrupt when a predefined number of
events have been counted; this is done by presetting the counter with the two's complement
value of the desired number of events.
17.8.2 MMCSM Prescaler
The built-in prescaler consists of a 8-bit modulus counter, clocked by the MCPSM output.
It is loaded with an 8-bit value every time the counter overflows or whenever the prescaler
output is selected as the clock source. This 8-bit value is stored in the MMCSMSCR bit
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PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
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