MC912DG128ACPVE Datasheet, PDF (250/478 Pages) Freescale Semiconductor, Inc – Upward compatible with M68HC11 instruction set

Freescale Semiconductor, Inc.
Enhanced Capture Timer
15.3.2 Pulse Accumulators
There are four 8-bit pulse accumulators with four 8-bit holding registers
associated with the four IC buffered channels. A pulse accumulator
counts the number of active edges at the input of its channel.
The user can prevent 8-bit pulse accumulators counting further than $FF
by PACMX control bit in ICSYS ($AB). In this case a value of $FF means
that 255 counts or more have occurred.
Each pair of pulse accumulators can be used as a 16-bit pulse
accumulator.
There are two modes of operation for the pulse accumulators.
15.3.2.1 Pulse Accumulator latch mode
The value of the pulse accumulator is transferred to its holding register
when the modulus down-counter reaches zero, a write $0000 to the
modulus counter or when the force latch control bit ICLAT is written.
At the same time the pulse accumulator is cleared.
15.3.2.2 Pulse Accumulator queue mode
When queue mode is enabled, reads of an input capture holding register
will transfer the contents of the associated pulse accumulator to its
holding register.
At the same time the pulse accumulator is cleared.
15.3.3 Modulus Down-Counter
The modulus down-counter can be used as a time base to generate a
periodic interrupt. It can also be used to latch the values of the IC
registers and the pulse accumulators to their holding registers.
The action of latching can be programmed to be periodic or only once.
Technical Data
250
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
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