lcd.asm

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY without ev

;+---------------------------------------------------------------------------+
;|                                                                           |
;| Copyright (C) 2002,  Tom De Rybel                                         |
;|                      [e-mail]                                   |
;|                                                                           |
;| This program is free software; you can redistribute it and/or             |
;| modify it under the terms of the GNU General Public License               |
;| as published by the Free Software Foundation; either version 2            |
;| of the License, or any later version.                                     |
;|                                                                           |
;| This program is distributed in the hope that it will be useful,           |
;| but WITHOUT ANY WARRANTY; without even the implied warranty of            |
;| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             |
;| GNU General Public License for more details.                              |
;|                                                                           |
;| You should have received a copy of the GNU General Public License         |
;| along with this program; if not, write to the Free Software               |
;| Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.                 |
;|                                                                           |
;|                                                                           |
;+---------------------------------------------------------------------------+
; LCD module test on the Cypress EZ-USB
; Writes a bit of text on a Hitachi HD44780-based standard 4X16 LCD module.
;
; The module operates in dumb 8-bit mode (without busyflag checking).
;
; Connections:   D0-D7: PC0-PC7
; ------------   RS:    PA4
; 	 	 EN:    PA5
; 		 R/#W:  GND
;
;
; Written by: Tom De Rybel [e-mail]
;
; This program has all the elegance of a mortally wounded warthog,
; so whatever you do, don't show this to anyone who knows how to code if you 
; decide to actually use it in the first place ;-). It works though.

	
;+-------------------------------------+
;| Declaration of the EZ-USB registers |
;+-------------------------------------+
;
.equ DPL1,	0x84
.equ DPH1,	0x85
.equ DPS,	0x86
.equ CKCON,	0x8E
.equ SPC_FNC,	0x8F
.equ EXIF,	0x91
.equ MPAGE,	0x92
.equ SCON1,	0xC0
.equ SBUF1,	0xC1
.equ EICON,	0xD8
.equ EIE,	0xE8
.equ EIP,	0xF8
		
.equ CPUCS,     0x7F92	
.equ PORTACFG, 	0x7F93
.equ PORTBCFG, 	0x7F94
.equ PORTCCFG, 	0x7F95
.equ OUTA,     	0x7F96	
.equ OUTB,     	0x7F97
.equ OUTC,     	0x7F98
.equ PINSA,    	0x7F99
.equ PINSB,    	0x7F9A
.equ PINSC,    	0x7F9B
.equ OEA,      	0x7F9C
.equ OEB,      	0x7F9D
.equ OEC,      	0x7F9E

.equ I2CS,	0x7FA5
.equ I2DAT,	0x7FA6

.equ USBCS,	0x7FD6				

;+--------------------+
;| Some LCD constants |
;+--------------------+
; 
.equ LINE1,	0x00
.equ LINE2,	0x40
.equ LINE3,	0x10
.equ LINE4, 	0x50


;+-------------------+
;| Interrupt vectors |
;+-------------------+
;
;Reset Vector
.org 0x0000
ljmp init


.org 0x0100
;+-------------------------+
;| Initialisation sequence |
;+-------------------------+
; 
init:
	;;mov	0x92, #0x7F	; tc, allows movx Ri to access ez-usb memory

	mov dptr, #PORTBCFG	; All pins are standard PB pins
	mov a, #00000000b
	movx @dptr, a
	
	mov dptr, #OEB		; Pin PB4 is an output pin
	mov a, #00010000b
	movx @dptr, a

	mov dptr, #PORTCCFG	; All pins are standard PC pins
	mov a, #00000000b
	movx @dptr, a
	
	mov dptr, #OEC		; Port PC is output
	mov a, #0xFF
	movx @dptr, a
	
	mov dptr, #PORTACFG	; All pins are standard PA pins
	mov a, #00000000b
	movx @dptr, a
	
	mov dptr, #OEA		; Pins PA4 and PA5 are output
	mov a, #00110000b	
	movx @dptr, a

	lcall init_LCD		; Initialize LCD module


;+--------------+
;| Main program |
;+--------------+
; 
begin:			
	mov r0, #LINE1
	mov dptr, #0x1000
	lcall write_string
	
	mov r0, #LINE2
	mov dptr, #0x1011
	lcall write_string
	
	mov r0, #LINE3
	mov dptr, #0x1022
	lcall write_string
	
	mov r0, #LINE4
	mov dptr, #0x1033
	lcall write_string

    blink:
	mov dptr, #OUTB
	mov a, #00010000b
	movx @dptr, a

	lcall  Wait100msec
	lcall  Wait100msec
	lcall  Wait100msec
	
	mov dptr, #OUTB
	mov a, #00000000b
	movx @dptr, a

	lcall  Wait100msec
	lcall  Wait100msec
	lcall  Wait100msec

	ljmp blink

;+------------------------------------+
;| High-level LCD routines            |
;|                                    |
;| R0 and DPTR are used and modified. |
;+------------------------------------+
; Store the LCD DD-RAM starting address for the line on which to write in R0.
; Store the begin address of the string in the DPTR
; The string must terminate with a '0'.
;
write_string:
	push acc		; Move the accumulator on the stack
	mov a, r0		; Build the correct command to write the string
	orl a, #10000000b	; starting address for the LCD DD-RAM
	mov r0, a

	lcall send_command

    loop_write_string:		    	
	mov a, #0x00		; Read the string from the code memory and 
	movc a, @a+dptr 	; write to the display until a terminating
	mov r0, a		; 0x00 is found
	jz end_write_string	

	lcall send_data

	inc dptr
	sjmp loop_write_string

    end_write_string:
	pop acc			; Retrieve the accumulator from the stack 
	
	ret


;+--------------------------+
;| Low-level LCD routines   |
;|                          |
;| R0 is used and modified. |
;+--------------------------+
; R0 carries the byte to be written to the display for both "send" routines
;
send_command:
	push acc		; Move the accumulator on the stack
	mov a, dpl		; Move the dptr on the stack
	push acc	
	mov a, dph
	push acc

	mov dptr, #OUTA		; Set RS low
	mov a, #00000000b
	movx @dptr, a
		
	mov dptr, #OUTC		; Write data to PC	
	mov a, r0	
	movx @dptr, a

	mov dptr, #OUTA		; Set EN high
	mov a, #00100000b
	movx @dptr, a
	
	mov r0, #0		; Kludge to fix R0 dependency in the delay
	lcall Wait10usec	; routines
	
	mov dptr, #OUTA		; Set EN low
	mov a, #00000000b
	movx @dptr, a

	pop acc			; Retrieve datapointer form the stack	
	mov dph, a		; This and the RET give sufficient delay
	pop acc			; to allow the display to process the data
	mov dpl, a
	pop acc			; Retrieve the accumulator from the stack 

	ret
	
	
send_data:
	push acc		; Move the accumulator on the stack
	mov a, dpl		; Move the dptr on the stack
	push acc	
	mov a, dph
	push acc

	mov dptr, #OUTA		; Set RS high
	mov a, #00010000b
	movx @dptr, a
		
	mov dptr, #OUTC		; Write data to PC	
	mov a, r0	
	movx @dptr, a

	mov dptr, #OUTA		; Set EN high
	mov a, #00110000b
	movx @dptr, a
	
	mov r0, #0		; Kludge to fix R0 dependency in the delay
	lcall Wait10usec	; routines
	
	mov dptr, #OUTA		; Set EN low
	mov a, #00010000b
	movx @dptr, a

	pop acc			; Retrieve datapointer form the stack	
	mov dph, a		; This and the RET give sufficient delay
	pop acc			; to allow the display to process the data
	mov dpl, a
	pop acc			; Retrieve the accumulator from the stack 

	ret

	
init_LCD:
	lcall Wait100msec	; Power-up reset delay safety

	mov r0, #00110000b	; Function set (8-bit interface)
	lcall send_command	
	
	mov r0, #0		; Kludge to fix R0 dependency in the delay routines
	lcall Wait1msec		; Wait for at least 4.1 ms (already 2 in the
	lcall Wait1msec		; send_command routine)
	
	mov r0, #00110000b	; Function set (8-bit interface)
	lcall send_command
		
	mov r0, #00110000b	; Function set (8-bit interface)
	lcall send_command
		
	mov r0, #00111000b	; Function set (8-bit interface, Dual(4) line,
	lcall send_command	; Display font)
	
	mov r0, #00001000b 	; Display off
	lcall send_command
	
	mov r0, #00000001b	; Display clear
	lcall send_command
	
	mov r0, #00000110b	; Entry mode set
	lcall send_command
	
	mov r0, #10000000b	; Line one, position one
	lcall send_command
	
	mov r0, #00001100b	; Display on
	lcall send_command
	
	ret
	
	
;+----------------------------------------------------------------------+
;| Timing loops taken from the buttons and lights example in USB Design |
;| by Example. These are needed by the LCD routines.                    |
;|                                                                      |
;| A, DPTR and R0 are used and modified.		                |
;+----------------------------------------------------------------------+
; 
Wait100msec:
        mov     r0, #100
Wait1msec:                      ; A delay loop
        mov     dptr,#-1200
More:   inc     dptr            ; 3 cycles
        mov     a,dpl           ; + 2
        orl     a,dph           ; + 2
        jnz     More            ; + 3 = 10 cycles x 1200 = 1msec
        djnz    r0, Wait1msec   ; 
        ret

Wait50usec:
	mov	r0, #5
Wait10usec:			
	mov	dptr, #-12
More2:	inc 	dptr
	mov	a, dpl
	orl	a, dph
	jnz	More2		; 10 cycles x 12 = 10usec 
	djnz	r0, Wait10usec	
	ret


.org 	0x1000
;+-------------------------------+
;| Some text-strings for the LCD |
;+-------------------------------+
; 
.db 	"<VUB Cyclotron> ",0x00
.db	"CombiLyse Mark I",0x00
.db	"Firmware rev. 1 ",0x00
.db     "Wolf Engineering",0x00