cc65/libsrc/serial/ser-kernel.s

;
; Ullrich von Bassewitz, 2003-04-15
;
; Common functions of the serial drivers
;

        .import         return0
        .importzp       ptr1
	.condes		ser_irq, 2		; Export as IRQ handler

        .include        "ser-kernel.inc"
        .include        "ser-error.inc"


;----------------------------------------------------------------------------
; Variables


.bss
_ser_drv:       .res    2      		; Pointer to driver

; Jump table for the driver functions.
.data
ser_vectors:
ser_install:   	jmp     return0
ser_uninstall: 	jmp     return0
ser_open:       jmp     return0
ser_close:      jmp     return0
ser_get:        jmp     return0
ser_put:        jmp     return0
ser_status:     jmp     return0
ser_ioctl:      jmp     return0
ser_irq:	.byte	$60, $00, $00	; RTS plus two dummy bytes

; Driver header signature
.rodata
ser_sig:        .byte   $73, $65, $72, SER_API_VERSION  ; "ser", version


;----------------------------------------------------------------------------
; unsigned char __fastcall__ ser_install (void* driver);
; /* Install the driver once it is loaded */


_ser_install:
       	sta     _ser_drv
  	sta	ptr1
  	stx     _ser_drv+1
  	stx    	ptr1+1

; Check the driver signature

        ldy     #.sizeof(ser_sig)-1
@L0:    lda     (ptr1),y
        cmp     ser_sig,y
        bne     inv_drv
        dey
        bpl     @L0

; Copy the jump vectors

        ldy     #SER_HDR::JUMPTAB
        ldx     #0
@L1:    inx                             ; Skip the JMP opcode
        jsr     copy                    ; Copy one byte
        jsr     copy                    ; Copy one byte
        cpy     #(SER_HDR::JUMPTAB + .sizeof(SER_HDR::JUMPTAB))
        bne     @L1

        jsr     ser_install             ; Call driver install routine

        ldy     ser_irq+2               ; Check high byte of IRQ vector
        beq     @L2                     ; Jump if vector invalid
	ldy	#$4C			; Jump opcode
	sty	ser_irq			; Activate IRQ routine
@L2:    rts

; Driver signature invalid

inv_drv:
        lda     #SER_ERR_INV_DRIVER
        ldx     #0
        rts

; Copy one byte from the jump vectors

copy:   lda     (ptr1),y
        sta     ser_vectors,x
        iny
        inx
        rts

;----------------------------------------------------------------------------
; unsigned char __fastcall__ ser_uninstall (void);
; /* Uninstall the currently loaded driver and return an error code.
;  * Note: This call does not free allocated memory.
;  */

_ser_uninstall:
        jsr     ser_uninstall           ; Call driver routine

	lda	#$60			; RTS opcode
	sta	ser_irq			; Disable IRQ entry point

        lda     #0
        sta     _ser_drv
        sta     _ser_drv+1              ; Clear the driver pointer

        tax
        rts                             ; Return zero