Advanced Parallel I/O - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 335

The function that outputs a character to the LCD and makes sure that the write operation
is complete is as follows:
putcLCD psha ; save a copy of the data

bset lcd_dat,lcd_RS ; select lcd Data register

bset lcd_dat,lcd_E ; pull E to high

anda #$F0 ; mask out the lower 4 bits

lsra ; match the upper 4 bits with the LCD

lsra ; data pins

oraa #$03 ; keep signal E and RS unchanged

staa lcd_dat ; send the upper 4 bits and E, RS signals

nop ; provide enough duration to the E signal

nop ; “

nop ; “

bclr lcd_dat,lcd_E ; pull the E signal low

pula ; retrieve the character from the stack

anda #$0F ; clear the upper 4 bits

lsla ; match the lower 4 bits with the LCD

lsla ; data pins

bset lcd_dat,lcd_E ; pull the E signal high

oraa #$03 ; keep E and RS unchanged

staa lcd_dat

nop

nop

nop

bclr lcd_dat,lcd_E ; pull E low to complete the write cycle

ldy #1 ; wait until the write operation is

jsr delayby50us ; complete

rts
The function that outputs a NULL-terminated string pointed to by the index register X is
as follows:
putsLCD ldaa 1, x 1 ; get one character from the string

beq donePS ; reach NULL character?

jsr putcLCD

bra putsLCD

donePS rts

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Example 7.5
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Write an assembly program to test the previous four subroutines by displaying the following
messages on two lines:
hello world!
LCD is working!
Solution: The program is as follows:
#include “c:\miniide\hcs12.inc”

lcd_dat equ PTK ; LCD data pins (PK5 , PK2)

lcd_dir equ DDRK ; LCD data direction port