Application example

AN420

12/15

Doc ID 2078 Rev 2

Hres .def 0bdh,0ffh,0ffh

;MS 2 bits of conversion result, and

;conversion flag

conv_f .equ 7;the MSB of Hres is the high resolution

;end of conversion flag

c1 .equ 6

;conversion step flags

c2 .equ 5

c3 .equ 4

c4 .equ 3

;using Hres

Lres .def 0beh,0ffh,0ffh

;LSB of conversion result

;************************** N O T E ***********************************************

;register W is used to save the accumulator contents

;in standard interrupt routines

;********************************************************************************

.org 880h

;one module only. Do not use this

;assembly directive if you organize

;your software in linkable modules

init ldi drb,1

ldi orb,1 ;PB0 is analog input

ldi ddrc,070h ;PC4..6 are open drain outputs

ldi orc,070h ;PC4..6 are push-pull outputs now

ldi drcs,0 ;assume PC7 is input with pull-up,

;no interrupt

ldi ior,10h ;enable interrupts

ldi Hres,0

reti ;initialize interrupt machine

conv

;this is an endless loop converting

;PB0 input with 10-bit resolution

;the first time here after reset,

;VN1=VN2=VN3=0

set conv_f,Hres

set c1,Hres

set 5,adcr ;start high resolution conversion

jrs conv_f,Hres,$

nop ;here the high resolution result is

;available in Hres-Lres

jp conv

adcint

ld w,a ;save accumulator

ld a,adr ;in accumulator conversion result

jrs c1,Hres,c1conv