參數(shù)資料
型號(hào): P83C524IFA
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 8-bit microcontrollers
中文描述: 8-BIT, MROM, 24 MHz, MICROCONTROLLER, PQCC44
封裝: PLASTIC, LCC-44
文件頁(yè)數(shù): 23/76頁(yè)
文件大小: 400K
代理商: P83C524IFA
1997 Dec 15
23
Philips Semiconductors
Product specification
8-bit microcontrollers
P83C524; P80C528; P83C528
11 TIMERS/COUNTERS
The P83C528 contains three 16-bit timer/counters, Timer
0, Timer 1 and Timer 2, and one 8-bit timer, the Watchdog
Timer T3. Timer 0, Timer 1 and Timer 2 may be
programmed to carry out the following functions:
measure time intervals and pulse durations
count events
generate interrupt requests.
11.1
Timer 0 and Timer 1
Timers 0 and 1 each have a control bit in TMOD SFR that
selects the timer or counter function of the corresponding
timer. In the timer function, the register is incremented
every machine cycle. Thus, one can think of it as counting
machine cycles. Since a machine cycle consists of 12
oscillator periods, the count rate is
1
12
of the oscillator
frequency.
In the counter function, the register is incremented in
response to a HIGH-to-LOW transition at the
corresponding external input pin, T0 or T1. In this function,
the external input is sampled during S5P2 of every
machine cycle. When the samples show a HIGH in one
cycle and a LOW in the next cycle, the counter is
incremented. Thus, it takes two machine cycles (24
oscillator periods) to recognize a HIGH-to-LOW transition.
There are no restrictions on the duty cycle of the external
input signal, but to ensure that a given level is sampled at
least once before it changes, it should be held for at least
one full machine cycle.
Timer 0 and Timer 1 can be programmed independently to
operate in one of four modes:
Mode 0 8-bit timer/counter with divide-by-32 prescaler
Mode 1 16-bit timer/counter
Mode 2 8-bit timer/counter with automatic reload
Mode 3 Timer 0: one 8-bit timer/counter and one 8-bit
timer. Timer 1: stopped.
When Timer 0 is in Mode 3, Timer 1 can be programmed
to operate in Modes 0, 1 or 2 but cannot set an interrupt
request flag and generate an interrupt. However, the
overflow from Timer 1 can be used to pulse the Serial Port
transmission-rate generator. With a 16 MHz crystal, the
counting frequency of these timer/counters is as follows:
in the timer function, the timer is incremented at a
frequency of 1.33 MHz (oscillator frequency divided by
12).
in the counter function, the frequency handling range for
external inputs is 0 Hz to 0.66 MHz.
Both internal and external inputs can be gated to the timer
by a second external source for directly measuring pulse
duration.
The timers are started and stopped under software control.
Each one sets its interrupt request flag when it overflows
from all logic 1's to all logic 0's (respectively, the automatic
reload value), with the exception of Mode 3 as previously
described.
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