; ---------------------------------------------------------------------
; 8749 to serial line EPROM reader for 8051 type processors.
;
; $Id: kbdbabel_8749_reader_8051.asm,v 1.1 2009/01/25 01:08:05 akurz Exp $
;
; Clock/Crystal: 24MHz
; alternatively 3.6864MHz or its multiples.
;
; Serial line connect:
; RxD - p3.0 (Pin 10 on DIL40, Pin 2 on AT89C2051 PDIP20)
; TxD - p3.1 (Pin 11 on DIL40, Pin 3 on AT89C2051 PDIP20)
;
; 87C49 connect:
; DB0-DB7 (pin12-19)	- p1.0-p1.7 (use 4k7 pull-ups on p1.0 and p1.1)
; P20-P22 (pin21-23)	- p3.2-p3.4
; T0,_RESET_ (pin1,4)	- p3.5
; XTAL1 (pin2)		- 3-4MHz
; EA (pin7)		- 18V
; Vdd (pin26)		- Vcc
; Vcc (pin40)		- Vcc
; Vss (pin20)		- GND
;
; Build using the macroassembler by Alfred Arnold
; $ asl -L kbdbabel_87c49_reader_8051.asm -o kbdbabel_87c49_reader_8051.p
; $ p2bin -l \$ff -r 0-\$7ff kbdbabel_87c49_reader_8051
; write kbdbabel_87c49_reader_8051.bin on an empty 27C256 or AT89C2051
;
; Copyright 2009 by Alexander Kurz
;
; This is free software.
; You may copy and redistibute this software according to the
; GNU general public license version 3 or any later verson.
;
; ---------------------------------------------------------------------

	cpu 8052
	include	stddef51.inc
	include kbdbabel_intervals.inc

;----------------------------------------------------------
; Variables / Memory layout
;----------------------------------------------------------
;------------------ octets
B20		sfrb	20h	; bit adressable space
B21		sfrb	21h
B22		sfrb	22h
BitCountL	equ	23h
BitCountH	equ	24h

;------------------ bits
billyTheBit	bit	B20.0	; demo

;------------------ stack
StackBottom	equ	50h	; the stack

;----------------------------------------------------------
; start
;----------------------------------------------------------
	org	0	; cold start
	ljmp	Start
;----------------------------------------------------------
; interrupt handlers
;----------------------------------------------------------
;----------------------------
;	org	03h	; external interrupt 0
;	ljmp	HandleInt0
;----------------------------
;	org	0bh	; handle TF0
;	ljmp	HandleTF0
;----------------------------
;	org	13h	; Int 1
;	ljmp	HandleInt1
;----------------------------
;	org	1bh	; handle TF1
;	ljmp	HandleTF1
;----------------------------
;	org	23h	; RI/TI
;	ljmp	HandleRITI
;----------------------------
;	org	2bh	; handle TF2
;	ljmp	HandleTF2

	org	033h

;----------------------------------------------------------
; helper, waste 20 cpu cycles
; note: call and return takes 4 cycles
;----------------------------------------------------------
nop20:
	nop
	nop
	nop
	nop
	nop
	nop

	nop
	nop
	nop
	nop
	nop
	nop
	nop
	nop
	nop
	nop

	ret


;----------------------------------------------------------
; helper, waste 200 cpu cycles
; note: call and return takes 4 cycles
;----------------------------------------------------------
nop200:
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20
	acall	nop20

	ret

;----------------------------------------------------------
; init uart with timer 1 as baudrate generator
; need 9600BPS
;
; --- dirty 9.6kbps
; precisely this is 9.6152kbps, 0.15% off the correct bitrate
; 9600BPS @24MHz -> tl1 and th1 = #243 with SMOD=1  ; (256-2*24000/384/9.6)
uart_t1_9600_24M	equ	243
;
;----------------------------------------------------------
uart_timer1_init:
	mov	scon, #050h	; uart mode 1 (8 bit), single processor
	orl	tmod, #020h	; M0,M1, bit4,5 in TMOD, timer 1 in mode 2, 8bit-auto-reload
	orl	pcon, #080h	; SMOD, bit 7 in PCON
	mov	th1, #uart_t1_9600_24M
	mov	tl1, #uart_t1_9600_24M
	clr	es		; disable serial interrupt
	setb	tr1

	clr	ri
	setb	ti

	ret

;----------------------------------------------------------
; Id
;----------------------------------------------------------
RCSId	DB	"$Id: kbdbabel_8749_reader_8051.asm,v 1.1 2009/01/25 01:08:05 akurz Exp $"

;----------------------------------------------------------
; main
;----------------------------------------------------------
Start:
	; -- init the stack
	mov	sp,#StackBottom
	; -- init UART and timer0/1
	acall	uart_timer1_init

	; -- disable interrupts int0
	clr	ea

	; -- clear all flags
	mov	B20,#0
	mov	B21,#0
	mov	B22,#0

	mov	BitCountL,#0
	mov	BitCountH,#0


	setb	p3.5

	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200

	clr	p3.5

	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200
	acall	nop200

; ----------------
loop:
	; -- clr t0
	clr	p3.5

	acall	nop200

	; -- write 11 address-bits
	mov	a,BitCountH
	mov	c,acc.0
	mov	p3.2,c
	mov	c,acc.1
	mov	p3.3,c
	mov	c,acc.2
	mov	p3.4,c
	mov	a,BitCountL
	mov	p1,a

	acall	nop200
	acall	nop200

	; -- set t0
	setb	p3.5
	acall	nop200


	; dirty hack: the 8749 seems not to be able to pull up 89c2051 lines
	mov	a,0ffh
	mov	p1,a

	acall	nop200
	acall	nop200

	; -- UART ready?
loop_waitfor_uart:
	jnb     TI,loop_waitfor_uart

	; -- read and send data
	mov	a,p1
	mov	sbuf,a
	clr	TI

	; -- inc addr
	mov	a,BitCountL
	inc	a
	mov	BitCountL,a
	jnz	loop_inc_done
	mov	a,BitCountH
	inc	a
	anl	a,#07h
	mov	BitCountH,a
	jnz	loop_inc_done
	; -- infinite Loop to stop here
loop_stop_here:
	clr	p3.5
	sjmp	loop_stop_here

loop_inc_done:	
	sjmp	loop

;----------------------------------------------------------
; Still space on the ROM left for the license?
;----------------------------------------------------------
LIC01	DB	"   Copyright 2009 by Alexander Kurz"
LIC02	DB	"   "
GPL01	DB	"   This program is free software; you can redistribute it and/or modify"
GPL02	DB	"   it under the terms of the GNU General Public License as published by"
GPL03	DB	"   the Free Software Foundation; either version 3, or (at your option)"
GPL04	DB	"   any later version."
GPL05	DB	"   "
GPL06	DB	"   This program is distributed in the hope that it will be useful,"
GPL07	DB	"   but WITHOUT ANY WARRANTY; without even the implied warranty of"
GPL08	DB	"   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the"
GPL09	DB	"   GNU General Public License for more details."
GPL10	DB	"   "
; ----------------
	end