nes-proj/platform/pc-6001/dev/rs232-asm.S

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;;;
;;;
;;; rs232-asm.S
;;;
;;; PC-6001 Architecture depend RS-232C implementation,
;;; uses a bunch of BIOS functions.
;;;
;;; @author Takahide Matsutsuka <markn@markn.org>
;;;
;;; $Id: rs232-asm.S,v 1.3 2007/11/28 09:39:30 matsutsuka Exp $
;;;
;; definitions of PC-6001 BIOS routines
_rs232c_initialize = 0x19bf
_buffer_out = 0x2627
_char_input_sub = 0x2642
_count_buffer = 0x26a2
_rs232c_intr_vector = 0xfa04
_subcpu_handshake_out = 0x0e8f
LOG = 0
CTK = 0
;; export symbols
.globl _rs232_arch_writeb
.globl _rs232_arch_poll
.globl _rs232_arch_init
.area _CODE
.if LOG
_hex:
.ascii "0123456789ABCDEF"
.if CTK
.globl _cputc_arch_asm
.else
.globl _libputc_asm
.globl _screen_offset
.endif
_rs232_arch_putc: ; a = data
ld hl, #0
ld (#_screen_offset), hl
push af
srl a
srl a
srl a
srl a
call _rs232_arch_putc_next1
pop af
and a, #0x0f
_rs232_arch_putc_next1:
ld hl, #_hex
_rs232_arch_putc_loop:
or a
jr z, _rs232_arch_putc_next2
inc hl
dec a
jr _rs232_arch_putc_loop
_rs232_arch_putc_next2:
ld a, (hl)
.if CTK
call _cputc_arch_asm
.else
call _libputc_asm
.endif
ret
.endif
;; ---------------------------------
;; void rs232_writeb(u8_t c)
;; Stack; retl reth c
;; AF__D_HL____
;; return void
;; ---------------------------------
_rs232_arch_writeb:
ld hl, #2
add hl, sp
ld d, (hl)
.if LOG
push de
ld a, #0x77 ; 'w'
.if CTK
call _cputc_arch_asm
.else
call _libputc_asm
.endif
pop de
;; ld a, d
;; push de
;; call _rs232_arch_putc
;; pop de
.endif
_rs232_arch_writeb_loop:
in a, (#0x81)
and a, #0x01
cp #0x01 ; TxRDY? 0x01/0x81/0x85
jr nz, _rs232_arch_writeb_loop
ld a, d
out (#0x80), a
ret
;; RS-232C interrupt routine
;; receive a byte and put it into the buffer
_rs232_arch_intr:
push bc
push af
push de
push hl
in a, (#0x81)
and a, #0x02 ; RxRDY?
jr z, _rs232_arch_intr_next ; no input
in a, (#0x80)
ld e, a
ld a, #0x01
call _buffer_out ; buffer output A=bufno, e=data
_rs232_arch_intr_next:
ld a, #0x0c
call _subcpu_handshake_out ; sub CPU handshake output A
call _rs232_arch_bufchk
pop hl
pop de
pop af
pop bc
ei
ret
_rs232_arch_bufchk:
ld a, #0x01
call _count_buffer ; count buffer available bytes -> A
cp #0x02 ; A >= 2?
ld a, #0x37 ; Rx enable
jr nc, _rs232_arch_bufchk_next ; buffer available bytes >= 2
ld a, #0x33 ; Rx disable
_rs232_arch_bufchk_next:
out (#0x81),a ; buf available=0x37, buf full=0x33
ret
;; ---------------------------------
;; unsigned char rs232_arch_poll(unsigned char *stat);
;; Stack; retl reth statl stath
;; AFBCDEHL____
;; return input byte (*stat == 0 if no input)
;; ---------------------------------
_rs232_arch_poll:
ld hl, #2
add hl, sp
ld e, (hl)
inc hl
ld d, (hl)
ld a, #0x01
ld (de), a
di
call _char_input_sub ; read from buffer
ei
push af
call _rs232_arch_bufchk ; buffer check
pop af
jr nz, _rs232_arch_poll_ret
xor a ; we have no data in the buffer
ld (de), a
jr _rs232_arch_poll_ret2
_rs232_arch_poll_ret:
.if LOG
call _libputc_asm
;; call _rs232_arch_putc
.endif
_rs232_arch_poll_ret2:
pop af
ld l, a
ret
;; ---------------------------------
;; void rs232_init(unsigned long ubr);
;; Stack; retl reth ubr1 ubr2 ubr3 ubr4
;; AFB_DEHL____
;; return void
;; ---------------------------------
_rs232_arch_init:
ld hl, #_rs232_arch_intr
di
ld (#_rs232c_intr_vector), hl
ei
;; S2 S1 PE P L2 L1 B2 B1
;; 0 1 0 0 1 1 1 1
;; 8-N-1 64x clock
ld b, #0x4f
call _rs232c_initialize
ld a, #0x37
out (#0x81), a
ret