EM73P461A
4-BIT MICRO-CONTROLLER FOR LCD PRODUCT
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 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 = 0F0AH
PULSE WIDTH MEASUREMENT MODE
* This specification are subject to be changed without notice.
12.27.2001
20
ELAN [ ELAN MICROELECTRONICS CORP ]
