AN1950

Sensors

Freescale Semiconductor

21

bset 3,porta

bclr 3,porta

;toggle E

bsr del100us

;data only requires 40us for LCD to execute

rts

;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

;

shiftA: shifts A into shift register and provides 8-bits to LCD

;

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shiftA: psha

mov #$08,BB

;will be shifting 8 bits

all8:

lsla

;get bit

bcc shift0

;if bit=0 then shift a 0

shift1: bset 4,porta

;otherwise shift a 1

bra shift

shift0: bclr 4,porta

;bit 4 is data to shift register

shift:

bclr 5,porta

;bit 5 is shift register clock

bset 5,porta

bclr 5,porta

;toggle CLK

dbnz BB,all8

;do all 8 bits

pula

rts

;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

;

lcdnibo: displays 1 character (0-9,A-F) based on low-nibble value in A

;

-------

lcdnibo: psha

;convert 4 bits from binary to ascii

add #$30

;add $30 (0-9 offset)

cmp #$39

;is it a number (0-9) ?

bls d0to9b

;if so skip

add #$07

;else add $07 = total of $37 (A-F offset)

d0to9b: bsr lcdchro

pula

rts

;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

;

lcdbyto: displays 2 characters based on hex value in A

;

-------

lcdbyto: psha

psha

;remember A (for low nibble)

lsra

;shift right 4 times

lsra

lsra

lsra

bsr lcdnibo

;high nibble

pula

and #$0F

bsr lcdnibo

;low nibble

pula

rts

;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

;

lcdstro: displays message ending in '@', but also sends commands to LCD

;

-------

lcdstro: psha

lda 0,x

lcon:

cmp #$80

;if ASCII >=$80

bhs iscmd

cmp #$1F

;or <=$1F then

bls iscmd

;assume it is a command to LCD

isdta: bsr lcdchro

;otherwise it is data to LCD

reuse1: aix #$0001

;next character

lda 0,x

;indexed by x

cmp #$40

;continue until

bne lcon

;character = '@'