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EM73A89B

4-BIT MICRO-CONTROLLER FOR LCD PRODUCT

ELAN Microelectronics 

TIMER MODE

EM73A89B

4-BIT MICRO-CONTROLLER FOR LCD PRODUCT

Preliminary

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

TimerB (TimerA )value n n+1 n+2 n+3 n+4 n+5 n+6 n+7

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

Under the pulse width measurement mode, the counter is incresed at the rising edge of internal pulse during

external timer/counter input (P8.1/TRGB, P8.3/TRGA) in high level, interrupt request is generated as soon as

timer/counter count overflow.

P8.1/TRGB(P8.3/TRGA)

Internal pulse

TimerB(TimerA) value

n n+1 n+2 n+3 n+4 n+5

PROGRAM EXAMPLE: Enable timerA by pulse width measurement mode.

LDIA #1100b ;

OUTA P28 ; Enable timerA with pulse width measurement mode.

* This specification are subject to be changed without notice.

8.16.2001 21

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