osd-contiki/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 1.2 2007/09/19 12:47:19 matsutsuka Exp $
;;;
;; definitions of PC-6001 BIOS routines
_rs232c_initialize = 0x19bf
_rs232c_char_output = 0x19e8
_char_input_sub = 0x2642
_rs232c_interrupt_sub = 0x0f64
;; export symbols
.globl _rs232_arch_writeb
.globl _rs232_arch_poll
.globl _rs232_arch_init
.area _CODE
;; ---------------------------------
;; void rs232_writeb(u8_t c)
;; Stack; retl reth c
;; AFBC__HL____
;; return void
;; ---------------------------------
_rs232_arch_writeb:
ld hl, #2
add hl, sp
ld a, (hl)
call _rs232c_char_output
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
jr nz, _rs232_arch_poll_ret
xor a ; we have no data in the buffer
ld (de), a
_rs232_arch_poll_ret:
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 b, #0x4f
call _rs232c_initialize
ret