HT47C20 Holtek Semiconductor Inc, HT47C20 Datasheet - Page 26

• Manufacturer Part Number: HT47C20
• Description: 8-Bit Microcontroller
• Manufacturer: Holtek Semiconductor Inc

The bit4~bit7 of ADCR decides which resistor
and capacitor compose an oscillation circuit and
input to TMRBH and TMRBL.
The TN0, TN1 and TN2 bits of TMRC define
the clock source of timer A. It is recommended
that the clock source of timer A use the system
clock, instruction clock or RTC prescaler clock.
The TON bit (bit 4 of TMRC) is set ²1² the timer
A and timer B will start counting until timer A
or timer B overflows, the timer/event counter
Example for RC type AD converter mode (Timer A overflow):
clr tmrc
clr adcr.1
clr intc1.4
mov a, low (65536-1000)
mov tmrbl, a
mov a, high (65536-1000)
mov tmrbh, a
mov a, 00010010b
mov adcr,a
mov a, 00h
mov tmrbl, a
mov a, 00h
mov tmrbh, a
mov a, 00110000b
mov tmrc, a
p10:
clr wdt
snz intcl.4
jmp p10
clr intcl.4
; set timer mode
; clear timer/event counter interrupt request flag
; give timer A initial value
; count 1000 time and then overflow
; RS0~CS0; set RC type ADC mode; set Timer A overflow
; give timer B initial value
; timer A clock source=T1 and timer on
; polling timer/event counter interrupt request flag
; clear timer/event counter interrupt request flag
; program continue
26
generates the interrupt request flag (TF ; bit 4
of INTC1) and the timer A and timer B stop
counting and reset the TON bit to ²0² at the
same time.
If the TON bit is ²1², the TMRAH, TMRAL,
TMRBH and TMRBL cannot be read or written
to. Only when the timer/event counter is off and
when the instruction ²MOV² is used could those
four registers be read or written to.
January 18, 2000
HT47C20