
PICDEM 2 User
’
s Guide
DS30374D-page 12
 2001 Microchip Technology Inc.
4.1  Main Routine
The main routine of 
a2d.asm
 handles the initialization of the PICmicro MCU 
and then waits in an infinite loop. The first few lines set PORTA as inputs and 
PORTB as outputs. InitializeAD, the Analog to Digital converter initialization 
routine, is then called. After the return from 
InitializeAD
, the routine waits 
for Tad (A/D conversion clock) and then starts an A/D conversion. The 
program then enters an infinite loop with the reading of the A/D and the 
updating of the LEDs handled by an interrupt routine 
Service_Int
.
Figure 4.2:  Main Routine
Start
Configure PORT B 
 Configure PORT A
(InitializeAD)
Wait for Tad
(SetupDelay)
Start A/D conversion
Service_Int
Initialize A/D module
A/D Complete
No
Yes