title	Module from library BASE_1 : CHNTAB
	name	('CHNTAB')
	maclib	baselib.lib

; Initialisation tables and validation for channel I/O

; Copyright (C)	Werner Cirsovius
;		Hohe Weide 44
;		D-20253 Hamburg
;		Tel.: +49-40-4223247

;		Version 1.0 February 1987

; ENTRY	Register C holds channel number 0 .. max

; EXIT	Carry set indicates error - channel out of range
;	On carry reset zero indicates channel opened if set
;	or still inactive if reset
;	Reg pair HL holds pointer to channel control block

	entry	@chacc

@chacc:
	ld	a,c		; Test max
	cp	max+1
	ccf
	ret	c
	push	bc
	ld	b,0
	ld	hl,chntab	; Get pointer
	add	hl,bc
	add	hl,bc
	add	hl,bc
	add	hl,bc
	pop	bc
	ld	a,(hl)		; Get active flag
	or	a
	ret

	dseg

chntab	equ	$
	rept	max+1
	db	-1		; Inactive flag
	ds	1		; Mode byte (0 write else read)
	ds	2		; Parameter block address
	endm

	end