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HT46R54A

A/D Type 8-Bit OTP MCU

Holtek Semiconductor 

HT46R53A/HT46R54A

Example: using Interrupt Method to detect end of conversion

clr EADI

; disable ADC interrupt

mov a,00000001B

mov ACSR,a

; setup the ACSR register to select fSYS/8 as the A/D clock

mov a,00100000B

mov ADCR,a

:

:

Start_conversion:

clr START

set START

clr START

clr ADF

set EADI

set EMI

:

:

:

; ADC interrupt service routine

ADC_ISR:

mov acc_stack,a

mov a,STATUS

mov status_stack,a

:

:

mov a,ADRH

mov adrh_buffer,a

mov a,ADRL

mov adrl_buffer,a

clr START

set START

clr START

:

:

EXIT_INT_ISR:

mov a,status_stack

mov STATUS,a

mov a,acc_stack

reti

; setup ADCR register to configure Port PB0~PB3 as A/D inputs

; and select AN0 to be connected to the A/D converter

; As the Port B channel bits have changed the following START

; signal (0-1-0) must be issued within 10 instruction cycles

; reset A/D

; start A/D

; clear ADC interrupt request flag

; enable ADC interrupt

; enable global interrupt

; save ACC to user defined memory

; save STATUS to user defined memory

; read conversion result high byte value from the ADRH register

; save result to user defined register

; read conversion result low byte value from the ADRL register

; save result to user defined register

; reset A/D

; start A/D

; restore STATUS from user defined memory

; restore ACC from user defined memory

Low Voltage Reset - LVR

There is a low voltage reset circuit (LVR) implemented in

the microcontrollers. The function can be enabled/dis-

abled by options.

If the supply voltage of the device is within the range

0.9V~VLVR such as changing a battery, the LVR will au-

tomatically reset the device internally.

The LVR includes the following specifications:

· The low voltage (0.9V~VLVR) has to remain in their

original state to exceed 1ms. If the low voltage state

does not exceed 1ms, the LVR will ignore it and do not

perform a reset function.

· The LVR uses the ²OR² function with the external RES

signal to perform chip reset.

The relationship between VDD and VLVR is shown below.

V DD

V O PR

5 .5 V 5 .5 V

V LV R

3 .0 V

2 .2 V

0 .9 V

Note: VOPR is the voltage range for proper chip

operation at 4MHz system clock.

Rev. 1.00

21

August 24, 2006

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