LCD timing issue?

RChapman — Fri, 20 Jan 2006 06:44:38 GMT

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Posted: Fri Dec 10, 2004 1:13 am

Hi Folks

I am trying to use 2 x 40 character LCD with HC908GP32 running with a 32.768kHz crystal.

The code below (in assembler) work fine in monitor mode, but, not when programmed into the micro.

I would like to use the busy flag from the LCD so that the code is faster and looks neater.

If anyone has any ideas I would like to hear them.

Note that I am only using Port C with an LED to try to work out where the program actually gets to.

When programmed, it looks like that LCD powers up correctly, then nothing.

Have fun

$BASE 10T ; sets number base to 10 unless otherwise specified.

; Setting labels for the ports
PORTA EQU $0000 ; address of PORTA
PORTB EQU $0001 ; address of PORTB
PORTC EQU $0002 ; address of PORTC
PORTD EQU $0003 ; address of PORTD
PORTE EQU $0008 ; address of PORTE
DDRA EQU $0004 ; data direction control for PORTA
DDRB EQU $0005 ; data direction control for PORTB
DDRC EQU $0006 ; data direction control for PORTC
DDRD EQU $0007 ; data direction control for PORTD
DDRE EQU $000C ; data direction control for PORTE
PTAPUE EQU $000D ; Pullup enable register for PORTA
;PTBPUE Pullup enable register for PORTB does not exist
PTCPUE EQU $000E ; Pullup enable register for PORTC
PTDPUE EQU $000F ; Pullup enable register for PORTD
;PTEPUE Pullup enable register for PORTE does not exist

CONFIG1 EQU $1F ; Configuration register address for COP etc

; Setting the labels for the clock speed of the chip
PCTL EQU $36 ; PLL control register
PBWC EQU $37 ; PLL bandwidth control register
PMSH EQU $38 ; PLL multiplier select register high
PMSL EQU $39 ; PLL multiplier select register low
PMRS EQU $3A ; PLL VCO range select register
PMDS EQU $3B ; PLL reference divider select register
; ******

; Setting other register labels
TBCR EQU $001C ; Timebase Control Register

ADSCR EQU $3C ; A/D Converter Status Control Register
ADR EQU $3D ; A/D data Register

; Uses PORT A data lines for the LCD and PORT E for control lines.
; R/W is on PORT D (0-write to, 1-read from LCD)

; PORT E
; Bit 0 will be the Enable line
; Bit 1 will be the RS (register select) line
; ie data (1) or function (0) mode

LCD EQU $0000 ; For sending info to LCD, actually PORT A

LCD_CONTROL EQU $0008 ; PORT E, controls LCD, the following values are sent here to
; operate LCD.
LCD_D_ON EQU %00000011 ; Sets PORT A value as character for LCD.
LCD_D_OFF EQU %00000010 ; Sends PORT A value as character to LCD.
LCD_F_ON EQU %00000001 ; Sets PORT A value as function command for LCD.
LCD_F_OFF EQU %00000000 ; Sends PORT A value as function command to LCD.

org $FFFE ; Sets the reset vector for programmed chip
FDB INIT

org $9000 ; program loads into memory from location specified

INIT LDA #$00 ; Simply initialisation values
LDX #$00

MOV #$31,CONFIG1 ; MCU runs w/o LVI and COP support

LCD_SETUP

MOV #$FF,DDRA ; Set PORTA as output
MOV #$FF,DDRC ; Set PORTC as output
MOV #$FF,DDRD ; Set PORTD as output
MOV #$03,DDRE ; Set PORT E as output (3 because there are only 2 bits).

MOV #$00,PORTC
MOV #$00,PORTD

LDA #$00
LOOP1 LDX #$00
DBNZX *
COM PORTC
DBNZA LOOP1

; IMPORTANT to set LCD as 4 bit, must send ONLY control code '0010' on the 4 data lines,
; THEN start sending the full 8 bit data/control codes in 2x4 bit nibbles, high nibble first!!!

MOV #$20,LCD ; Sets LCD to 4 bit data
MOV #LCD_F_ON,LCD_CONTROL ; Do NOT use the sub routine LCD_FUNCTION here,
NOP ; as it will send 2x4 bit nibbles.
MOV #LCD_F_OFF,LCD_CONTROL

LDA #$00
LOOP2 LDX #$00
DBNZX *
COM PORTC
DBNZA LOOP2

MOV #$28,LCD ; Sets display as 4 bit data, 2 line, 5x7 matrix
;JSR LCD_FUNCTION

LDA #$00
LOOP3 LDX #$00
DBNZX *
COM PORTC
DBNZA LOOP3

MOV #$01,LCD ; Clears display and sends cursor home
JSR LCD_FUNCTION

MOV #$02,LCD ; Sends cursor and display home
JSR LCD_FUNCTION

MOV #$0F,LCD ; Turns display ON, cursor ON, Blink ON.
JSR LCD_FUNCTION

LDHX #LCD_OK ; Load HX regs with location of message
LDA #'^' ; Load A with ascii value of '^'

TEXT_1 MOV X+,LCD ; Copy the contents of location HX to LCD (PORT A). Note, also increments X.
CMP LCD ; Compare LCD with A
BEQ END_LCD_SETUP ; Exits text routine if reach end-of-text marker '^'
JSR LCD_DATA ; Puts text onto LCD screen
JMP TEXT_1

END_LCD_SETUP

JMP *

;*******

LCD_FUNCTION
LDA LCD

STA LCD ; Moves accumulator to location LCD, loads high 4 bits into the LCD screen
MOV #LCD_F_ON,LCD_CONTROL
NOP
MOV #LCD_F_OFF,LCD_CONTROL
JSR LCD_DELAY

NSA ; nibble swaps the accumulator

STA LCD ; Moves accumulator to location LCD, loads high 4 bits into the LCD screen
MOV #LCD_F_ON,LCD_CONTROL
NOP
MOV #LCD_F_OFF,LCD_CONTROL
JSR LCD_DELAY

RTS
;*******

LCD_DATA
PSHA

LDA LCD ; Moves accumulator to location LCD, loads high 4 bits into the LCD screen
MOV #LCD_D_ON,LCD_CONTROL
NOP
MOV #LCD_D_OFF,LCD_CONTROL
JSR LCD_DELAY

NSA ; nibble swaps the accumulator

STA LCD ; Moves accumulator to location LCD, loads high 4 bits into the LCD screen
MOV #LCD_D_ON,LCD_CONTROL
NOP
MOV #LCD_D_OFF,LCD_CONTROL
JSR LCD_DELAY

PULA

RTS
;*******

LCD_DELAY
MOV #$00,DDRA ; Set PORT A as input
MOV #$FF,PORTD ; Sets LCD to read mode
BRSET 7,PORTA,*
MOV #$00,PORTD ; Sets LCD to write mode
MOV #$FF,DDRA ; Set PORTA to output

RTS
;*******

Org $8000
LCD_OK EQU $8000
DB '<LCD OK>^'

Posted: Sun Dec 12, 2004 10:30 pm

Not to sure but don't you need to reset the stack pointer.

Posted: Mon Dec 13, 2004 8:18 am

am reasonably sure that the stack pointer does not need initilizing and as I only do one set of push/pulls, reseting the stack pointer should not be an issue.

Regardless, the program works with a timed LCD_DELAY and the same push/pulls.

Posted: Mon Dec 13, 2004 7:13 pm

Hi,

What's your configuration (ports level + XTAL) in Monitor mode ?

Cheers

Posted: Fri Dec 17, 2004 11:16 am

Helllo,

in your delay routine you have to togggle the ECLK Pin everytime you read the dataport to get actual data. So you have to use a loop ta wait until D7 is cleared.

LCD_DELAY
MOV #$00,DDRA ; Set PORT A as input
MOV #$FF,PORTD ; Sets LCD to read mode
---> toggle ECLK here
BRSET 7,PORTA,* and go back to LCD_DELAY to read again
MOV #$00,PORTD ; Sets LCD to write mode
MOV #$FF,DDRA ; Set PORTA to output

RTS

Posted: Thu Apr 07, 2005 6:58 am

Thanks for the help folks, it works wonderfully now.

I finally found the time to sit down and work through it all. There were a pile of things that just weren't quite right, mostly with the way I was thinking about it.

Have fun

Message Edited by RChapman on 01-19-2006 04:47 PM

topic LCD timing issue? in 8-bit Microcontrollers

LCD timing issue?