HTG12B0 データシートの表示（PDF） - Holtek Semiconductor

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HTG12B0

4-Bit Microcontroller

Holtek Semiconductor 

HTG12B0

Interrupt

The HTG12B0 provides both TIMER and RTC

interrupt modes. The DI and EI instructions

are used to disable and enable the interrupts.

When the RTC is activated during enable inter-

rupt mode and the program is not within a

CALL subroutine, this causes a subroutine call

to location 8 and reset the interrupt latch.

Likewise when the timer flag is set in the en-

able interrupt mode and the program is not

within a CALL subroutine, the TIMER inter-

rupt is activated. This cause a subroutine call to

location 4 and resets the timer flag. If both

TIMER and RTC interrupts arrive at the same

time, the RTC one will be serviced first.

When running under a CALL subroutine or DI

the interrupt acknowledge is on hold until the

RET or EI instruction is invoked. The CALL in-

struction should not be used within an inter-

rupt routine as unpredictable results may

occur. If within a CALL subroutine both

TIMER and RTC interrupt occur, no matter

what order they arrive in, the RTC interrupt

will be serviced first after leaving the CALL

subroutine. This also applies if the two inter-

rupt arrive at the same time.

The interrupts are disabled by a hardware re-

set or a DI instruction. They remain disabled

until the EI instruction is executed.

Initial reset

The HTG12B0 provides a RES pin for system

initialization. This pin is equipped with an in-

ternal pull high resistor and in combination

with an external 0.1m~1mF capacitor, it pro-

vides an internal reset pulse of sufficient length

to guarantee a reset to all internal circuits. If

the reset pulse is generated externally, the RES

pin must be held low at least 5ms.

When RES is active, the internal block will be

initialized as shown below:

PC

000H

TIMER

Stop

Timer flag

Reset (low)

SOUND

Sound off and One sing

mode

Output port A High (or floating state)

LCD output

Enable

BZ and BZ output Low level

ROMB

XX00B

RAMB

X000B

LCDC

1100B

HALT

This is a special feature of the HTG12B0 to inter-

rupt the chip¢s normal operation and reduce

power consumption. When a HALT is executed

the following happens ...

· The system clock will be stopped

· The contents of the on-chip RAM and regis-

ters remain unchanged

· RTC oscillator keeps on running

· BZ and BZ maintain low level output

The system can leave the HALT mode through

initial reset or RTC interrupt or wake-up from

the following entry of program counter value.

Initial reset: 00H

Wake-up: next address of the HALT instruction

11

September 8, 1999

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