Motorola 009 User Manual download pdf (Page 21)

System Overview

DSP Subsystem Code

MOTOROLA

SHI Port Usage

2-9

with the data for the pins. Next, the accumulator is ORed with register x0

thus

combining the GPIO port data with the GPIO port settings. The fully constructed GPIO

port word is moved to the GPIO register and the external signals respond accordingly.

Finally, an RTI instruction is executed and program flow returns to the main program.

Example 2-2

DSP Application Software

page 132,66,3,3

opt cex,mex,cc,mu

title 'main'

section main

nolist

include 'ioequ.asm'

list

comment ~

********************************************************************************

Start of assembly code

********************************************************************************

org p:0

jmp <main ; jmp to main out of reset

org p:$24 ; receive FIFO not empty

jsr SHI_ISR ; jsr to SHI_ISR

org p:$2a ; receive FIFO overrun

jsr SHI_ISR ; jsr to SHI_ISR

org p:$80

main

movep #$000f00,x:<<GPIOR ; set all GPIO to outputs

bset #HRIE0,x:HCSR ; enab intrpt for FIFO not empty

movep #$003000,x:IPR ; set interrupt priority for SHI

andi #$fc,mr ; enable interrupts

jmp * ; idle state for main program

SHI_ISR

movep x:<<HRX,x0 ; get new received data

move #$000f00,a ; GPIO port val

or x0,a ; update data portion

movep a1,x:<<GPIOR ; output new GPIOR val

rti

endsec

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Motorola 009 User Manual Page 21

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