HT46R92 datasheet(31/61 Pages) HOLTEK

31 / 61 page

HT46R92

Rev. 1.10

November 5, 2008

F F E H

(

)

A / D C o n v e r s i o n

R e s u l t

F F F H

F F D H

0 3 H

0 2 H

0 1 H

0 . 5 L S B

4 0 9 3 4 0 9 4 4 0 9 5 4 0 9 6

A n a l o g I n p u t V o l t a g e

1 . 5 L S B

V R E F

4 0 9 6

Ideal A/D Transfer Function

; ADC interrupt service routine

ADC_ISR:

mov

acc_stack,a

; save ACC to user defined memory

mov

a,STATUS

mov

status_stack,a

; save STATUS to user defined memory

mov

a,ADRL

; read low byte conversion result value

mov

adrl_buffer,a

; save result to user defined register

mov

a,ADRH

; read high byte conversion result value

mov

adrh_buffer,a

; save result to user defined register

EXIT_INT_ISR:

mov

a,status_stack

mov

STATUS,a

; restore STATUS from user defined memory

mov

a,acc_stack

; restore ACC from user defined memory

reti

A/D Transfer Function

As the device contain a 12-bit A/D converter, its

full-scale converted digitised value is equal to FFFH.

Since the full-scale analog input value is equal to the

VDD voltage, this gives a single bit analog input value of

VDD/4096. The diagram show the ideal transfer function

between the analog input value and the digitised output

value for the A/D converter.

Note that to reduce the quantisation error, a 0.5 LSB off-

set is added to the A/D Converter input. Except for the

digitised zero value, the subsequent digitised values will

change at a point 0.5 LSB below where they would

change without the offset, and the last full scale digitised

value will change at a point 1.5 LSB below the VDD level.

HT46R92 Datasheet(PDF) 31 Page - Holtek Semiconductor Inc

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