/****************************************************************************
   
    OS/A65 Version 2.0.0
    Multitasking Operating System for 6502 Computers
    Generic nulldevice

    Copyright (C) 1989-1998 Andre Fachat 

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

****************************************************************************/


#define   ANZINSTR  16

          .(
          .word nulend
          jmp nulprg
          .asc "nuldev",0

	.data
anzinstr  .byt 0
instr     .dsb ANZINSTR
	.text

nulprg    cmp #DC_RES
          bne sp1
          
          ldy #0
          sty anzinstr
          lda #<-1
ni1       sta instr,y
          iny
          cpy #ANZINSTR
          bcc ni1
          clc
          rts

sp1       cmp #DC_IRQ
          bne sp2

          ldy #0
spil      ldx instr,y
          bmi spiln
          jsr GETC
          bcc spil
          cmp #E_EOF
          bne spiln

          ldx instr,y
          lda #SC_NUL
          jsr STRCMD
          lda #<-1
          sta instr,y

spiln     iny
          cpy #ANZINSTR
          bcc spil
          clc
	lda #E_NOIRQ
          rts

sp2       cmp #DC_RX_OFF
          beq nlnotimp
          cmp #DC_TX_OFF
          bne sp3
          ldy #0              ; rxoff
rxo1      ldx instr,y
          lda #SC_NUL
          jsr STRCMD
          lda #<-1
          sta instr,y
          iny
          cpy #ANZINSTR
          bcc rxo1
          bcs ok

sp3       cmp #DC_RX_ON
          beq nlnotimp
          cmp #DC_TX_ON
          bne sp5

ok        lda #0
          .byt $2c
nlnotimp  lda #E_NOTIMP
          .byt $2c
nldevon   lda #E_DON
          cmp #1
          rts

sp5       cmp #DC_GS
          bne nlnotimp
          ldx #0
sp5a      lda instr,x
          bpl sp5n
          tya
          sta instr,x
          clc
          rts
sp5n      inx
          cpx #ANZINSTR
          bcc sp5a
          bcs nldevon

#undef ANZINSTR

nulend    .)