EM73PA88A
4-BIT MICRO-CONTROLLER FOR LCD PRODUCT
TIMER/COUNTER FUNCTION
Timer/counterA,B are programmable for timer, event counter and pulse width measurement mode. Each
timer/counter can execute any of these functions independently.
EVENT COUNTER MODE
under event counter mode, the timer/counter is increased by one at any rising edge of P8.1/TRGB for timerB
(P8.3/TRGA for timer A). When timerB (timerA) counts overflow, it will provide an interrupt request
TRGB (TRGA) to interrupt control unit.
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
Under timer mode ,the timer/counter is increased by one at any rising edge of internal pulse. User can choose
up to 4 types of internal pulse rate by setting IPSB for timerB (IPSA for timerA).
When timer/counter counts overflow, an interrupt request will be sent 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 LXlN=32KHz
LDIA #0100B;
EXAE; enable mask 2
EICIL 110111b; interrupt latch ←0, enable EI
LDIA #0Ah;
STATAL;
LDIA #00h;
STATAM;
LDIA #0Fh;
STATAH;
LDIA #1000B;
OUTA P28; enable timerA with internal pulse rate: LXIN/23 Hz
NOTE: The preset value of timer/counter register is calculated as following procedure.
Internal pulse rate: LXIN/23 ; LXIN = 32KHz
The time of timer counter count one = 23 /LXIN = 8/32768=0.244ms
The number of internal pulse to get timer overflow = 60 ms/ 0.244ms = 245.901= 0F6h
The preset value of timer/counter register = 1000h - 0F6h = F0Ah
PULSE WIDTH MEASUREMENT MODE
* This specification are subject to be changed without notice.
10.8.2001
21
ELAN [ ELAN MICROELECTRONICS CORP ]
