MC68HC705P9 Datasheet, PDF (101/160 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Timer
Operation
TCAP
EDGE
SELECT/
DETECT
LOGIC
IEDG
INTERNAL
CLOCK
(XTAL ÷ 2)
÷4
INTERNAL
DATA BUS
ICRH
ICRL
TRH
TRL
ATRH
ATRL
16-BIT COUNTER
16-BIT COMPARATOR
OCRH
OCRL
TIMER OVERFLOW
PIN
CONTROL
LOGIC
TCMP
OLVL
OCIE
OCF
TOIE
TOF
ICIE
ICF
TIMER
INTERRUPT
REQUEST
Figure 9-1. Timer Block Diagram
9.4 Operation
The timing reference for the input capture and output compare functions
is a 16-bit free-running counter. The counter is preceded by a divide-by-
four prescaler and rolls over every 2¹⁸ cycles. Timer resolution with a 4-
MHz crystal is 2 µs. Software can read the value in the counter at any
time without affecting the counter sequence.
Because of the 16-bit timer architecture, the I/O registers for the input
capture and output compare functions are pairs of 8-bit registers.
MC68HC705P9 — Rev. 4.0
MOTOROLA
Timer
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Technical Data
101