HT85F2270 datasheet(161/226 Pages) HOLTEK

161 / 226 page

Rev. 1.00

161 of ��6

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

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 ADCK2~ADCK0 in the

ADCR1 register and select the converted data storage format using the ADRFS bit.

■

Step 2

Enable the A/D by clearing the ADOFF bit in the ADCR0 register to zero and select the PGA

gain using the ADPGA register according to the dynamic range of the analog input signal.

■

Step 3

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

the ACS4~ACS0 bits which are also contained in the ADCR1 and ADCR0 register.

■

Step 4

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

ACE7~ACE0 bits in the ADCR2 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, EAL, and

the A/D converter interrupt bit, EADC, must both 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 ADCR0 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

ADCR0 register can be polled. The conversion process is complete when this bit changes from

high to low. When this occurs 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 ADCR0 register is used, the interrupt enable step above can be omitted.

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