i2c.asm

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

	lcall Inc_dptr1Write_EEProm

	mov R0, #0x01		; Write 01h (1 byte to be loaded)
	lcall Inc_dptr1Write_EEProm

	mov R0, #0x7F		; Write 7Fh (Load to the CPUCS register)
				; The CPUCS register is located at 7F92h
	lcall Inc_dptr1Write_EEProm

	mov R0, #0x92		; Write 92h
	lcall Inc_dptr1Write_EEProm

	mov R0, #0x00		; Write 00h (Take the 8051 out of reset)
	lcall Inc_dptr1Write_EEProm	
			
	;; That's all folks!
	
	ret

	
;+--------------------------------------------------------+
;| dptr1 switchover and increment plus writing the EEProm |
;|                                                        |
;| dptr1 is used and modified                             | 
;+--------------------------------------------------------+
; This is a code-size reducing sub-routine for the SelfLoader routine.
; It is pretty useless outside that context.
; 
Inc_dptr1Write_EEProm:
	mov R1, DPH1
	mov R2, DPL1
	inc DPS
	inc dptr
	inc DPS
	lcall EEProm_write
	ret	
		
				
; These I2C routines are based upon the Cypress application note:	
; "Programming a 24L00 EEPROM using the EZ-USB I睠 Port".
;
; These routines assume an EEProm wired with A0=1, A1=0, and A2=0. 
; For different setups, modify the nessesary EEProm address fields in these
; routines. (The affected bytes are 10100010 (write) and 10100011 (read)) 
 
;+--------------------------------------+
;| High-level I2C EEProm Write routines |
;|                                      |
;| R0, R1, and R2 are used and modified |	 
;+--------------------------------------+
; R0 contains the source data word. 
; R1 (MSB) and R2 (LSB) the destination addresses
;
EEProm_write:
	push acc		; Save the accumulator on the stack
	mov a, dph		; Save the dptr on the stack
	push acc
	mov a, dpl
	push acc
				
	lcall stop_check		; Make sure stop is not in progress

	mov dptr, #I2CS		; Set the start bit
	mov a, #10000000b	; B7 = start bit
	movx @dptr, a

	mov dptr, #I2DAT	; Write the EEProm address 10100010 and
	mov a, #10100010b	; indicate write operation (B0=0)
	movx @dptr, a
	lcall wait_done

	mov dptr, #I2DAT	; Send the EEProm "MSB word address"
	mov a, R1
	movx @dptr, a
	lcall wait_done

	mov dptr, #I2DAT	; Send the EEProm "LSB word address"
	mov a, R2
	movx @dptr, a
	lcall wait_done

	mov dptr, #I2DAT	; Send the actual data
	mov a, R0
	movx @dptr, a
	lcall wait_done

	mov dptr, #I2CS		; Send stop. This initiates the internal
	mov a, #01000000b	; write cycle
	movx @dptr, a
	lcall stop_check		; Wait for completion of stop

;Wait for the erase/write cycle to complete. This is done by sending
;a write command byte and checking the ACK bit. The EEProm will not respond
; (ACK) while a write cycle is in progress.
;
write_wait:
	mov dptr, #I2CS		; Send start
	mov a, #10000000b	; B7 = start bit
	movx @dptr, a
	mov dptr, #I2DAT	; Write a command byte
	mov a, #10100010b	; EEProm write
	movx @dptr, a
	lcall wait_done
	mov dptr, #I2CS		; Send stop
	mov a, #01000000b
	movx @dptr, a
	lcall stop_check	; Wait for completion of stop

	mov dptr, #I2CS		; Check the ACK bit
	movx a,@dptr
	jnb acc.1, write_wait	; Keep trying until ACK=1

	pop acc			; Restore the dptr and accumulator
	mov dpl, a
	pop acc
	mov dph, a
	pop acc
			
	ret


;+--------------------------------------+
;| Low-level I2C supportive routines    |
;|                                      |
;| R0, A and DPTR are used and modified |	 
;+--------------------------------------+
; 	
stop_check:
	mov dptr, #I2CS		; Check the stop bit in I2CS
stck:	
	movx a, @dptr
	jb acc.6, stck
	
	ret	 


wait_done:	
	mov dptr, #I2CS		; Check the done bit in I2CS
wado:
	movx a,@dptr
	jnb acc.0,wado

	ret

	
;+------------------------------------+
;| 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 comand 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 	"EZ-USB I2C test ",0x00
.db	" With an 24C64  ",0x00
.db	" Serial EEPROM  ",0x00
.db     "Wolf Engineering",0x00