HT46R0664 datasheet(60/92 Pages) HOLTEK

60 / 92 page

Rev. 1.00

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Rev. 1.00

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HT46R0664

Enhanced A/D+LCD Type 8-Bit OTP MCU

A/D Input Pins

All of the A/D analog input pins are pin-shared with the I/O pins on Port A, B, E, F. Bits

PCR7~PCR0 in the ANCSR0 register and PCR11~PCR8 in the ANCSR1 register, determine

whether the input pins are setup as normal input/output pins or whether they are setup as analog

inputs. In this way, pins can be changed under program control to change their function from normal

I/O operation to analog inputs and vice versa. Pull-high resistors, which are setup through register

programming, apply to the input pins only when they are used as normal I/O pins, if setup as A/D

inputs the pull-high resistors will be automatically disconnected. Note that it is not necessary to first

setup the A/D pin as an input in the I/O port control registers to enable the A/D input as when the

PCRn bits enable an A/D input, the status of the port control register will be overridden.

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

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

programming the PCR11~PCR0 bits in the ANCSR0 and ANCSR1 register.

● Step 3

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

● Step 4

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

the ACS3~ACS0 bits which are also contained in the 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, the

INTC0 interrupt control register must be set to “1”, the A/D converter interrupt bit, ADE, must

also be set to “1”.

● 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

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 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.

HT46R0664 Datasheet(PDF) 60 Page - Holtek Semiconductor Inc

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