EM73962A
4-BIT MICROCONTROLLER
TIMER/COUNTER FUNCTION
Timer/counterA can be programmable for timer, event counter and pulse width measurement. Each timer/
counter can execute any one of these functions independly.
EVENT COUNTER MODE
For event counter mode, timer/counter increases one at any rising edge of P8.1/TRGB for timerB (P8.3/
TRGA for timer A). When timerB (timerA) counts overflow, it will give interrupt control an interrupt request
TRGB (TRGA).
P8.1/TRGB (P8.3/TRGA)
TimerB (TimerA) value n
n+1
n+2
n+3
n+4
n+5
n+6
PROGRAM EXAMPLE: Enable timerA with P28
LDIA#0100B;
OUTA P28; Enable timerA with event counter mode
TIMER MODE
For timer mode ,timer/counter increase one at any rising edge of internal pulse. User can choose 4 kinds
of internal pulse rate by setting IPSB for timerB (IPSA for timerA).
When timer/counter counts overflow, TRGB (TRGA) will be generated to interrupt control unit.
Internal pulse
n
n+1
n+2
n+3
n+4
n+5
n+6
n+7
TimerB (TimerA )value
PROGRAM EXAMPLE:To generate TRGA interrupt request after 60 ms with system clock fc=4MHz
LDIA
#0100B
;
EXAE
; enable mask 2
EICIL
LDIA
110111B
#06H
; interrupt latch ←0, enable EI
;
STATAL
LDIA
STATAM
LDIA
;
;
;
;
#01H
#0FH
STATAH
LDIA
OUTA
;
;
#1000B
P28
; enable timerA with internal pulse rate: fc/210 Hz
NOTE: The preset value of timer/counter register is calculated as following procedure.
Internal pulse rate: fc/210 ; fc = 4MHz
The time of timer counter count one = 210 /fc = 1024/4000=0.256ms
The number of internal pulse to get timer overflow = 60 ms/ 0.256ms = 234.375 = 0EAH
The preset value of timer/counter register = 1000H - 0EAH = 0F16H
PULSE WIDTH MEASUREMENT MODE
* This specification are subject to be changed without notice.
10.8.2001
16
ELAN [ ELAN MICROELECTRONICS CORP ]
