HT45F43 datasheet(79/152 Pages) HOLTEK

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The A/D converter has its own reference voltage pin, VREF, however the reference voltage can also be

supplied from the power supply pin, a choice which is made through the VRSEL bit in the ACSR

Summary of A/D Conversion Steps

The following summarises the individual steps that should be executed in order to implement an A/D

conversion process.

· Step 1

Select the required A/D conversion clock by correctly programming bits ADCS2~ADCS0 in the

ACSR register.

· Step 2

Enable the A/D by clearing the ADONB bit in the ACSR register to zero.

· Step 3

Select which channel is to be connected to the internal A/D converter by correctly programming the

ACS2~ACS0 bits which are also contained in the ADCR register.

· Step 4

Select which pins are to be used as A/D inputs and configure them by correctly programming the

PCR5~PCR0 bits in the ADPCR register.

· Step 5

If the interrupts are to be used, the interrupt control registers must be correctly configured to ensure

the A/D converter interrupt function is active. The master interrupt control bit, EMI, Mulit-function

interrupt bit, and the A/D converter interrupt bit, EADI, must all be set high to do this.

· Step 6

The analog to digital conversion process can now be initialised by setting the START bit in the

ADCR register from low to high and then low again. Note that this bit should have been originally

cleared to zero.

· Step 7

To check when the analog to digital conversion process is complete, the EOCB bit in the ADCR

the A/D data registers ADRL and ADRH can be read to obtain the conversion value. As an

alternative method, if the interrupts are enabled and the stack is not full, the program can wait for an

A/D interrupt to occur.

Note: When checking for the end of the conversion process, if the method of polling the EOCB bit in

the ADCR register is used, the interrupt enable step above can be omitted.

The accompanying diagram shows graphically the various stages involved in an analog to digital

conversion process and its associated timing. After an A/D conversion process has been initiated by

the application program, the microcontroller internal hardware will begin to carry out the conver-

sion, during which time the program can continue with other functions. The time taken for the A/D

conversion is 16tADCK where tADCK is equal to the A/D clock period.

Programming Considerations

During microcontroller operations where the A/D converter is not being used, the A/D internal

circuitry can be switched off to reduce power consumption, by setting bit ADONB high in the ACSR

what analog voltage is applied to their input lines. If the A/D converter input lines are used as normal

I/Os, then care must be taken as if the input voltage is not at a valid logic level, then this may lead to

some increase in power consumption.

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

HT45F43 数据表(PDF) 79 Page - Holtek Semiconductor Inc

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