;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
;			 S E T Z 3
;			 for  ZPM3
;			by Simeon Cran
;			   30/3/92
;
; This program automatically sets the system environment address in the ZPM3
; SCB for Z3PLUS users. Certain advanced ZCPR facilities such as wheel
; protection of files will then be activated.
;
; Z3PLUS users should run SETZ3.COM once when they start up Z3PLUS and again
; when returning to regular (non-Z-System) operation. When run after Z3PLUS
; is started, the SCB environment address word is set with the ZCPR environment
; address. When run after returning to regular operation, the SCB environment
; address word is cleared to 0000h.
;
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

;===============================================================================

BDOS	equ	5
deffcb	equ	5ch
SCBfunc	equ	31h	; Get/Set SCB function number
SCBoff	equ	3bh	; Offset in SCB to get SCB base page
Z3ENVoff equ	83h	; Offset in SCB base page of the ZCPR system
			;  environment pointer.

	jp	start	; Jump over general data
	db	'Z3ENV'
	db	1
Z3ENV:	dw	0
	dw	0
HELPmsg:
	db	' SYNTAX:'
	db	10,13
	db	'  SETZ3'
	db	10,13
	db	'              Sets the ZCPR environment address in the SCB,'
	db	10,13
	db	'              or else clears it if not running ZCPR.'
	db	10,13
	db	'  SETZ3 //    Displays this brief help message'
	db	'$'

HELP:	ld	de,HELPmsg
MSGexit:
	ld	c,9
	call	bdos
	rst	0

start:	; Get the address of the SCB environment address pointer.
	ld	de,(Z3ENV)
	ld	a,d
	or	e		; Has it been set by Z3PLUS?
	jr	nz,Zinstall	; Jump if it has
	ex	de,hl
	ld	a,d
	or	e		; Was it in HL instead?
	jr	nz,Zinstall
Zinstall:	; DE holds 0 if uninstalling, otherwise the address of the
		;  ZCPR evironment descriptor.
	push	de
	ld	c,SCBfunc
	ld	de,SCBPB
	call	bdos		; Get base page of SCB
	ld	h,a
	ld	l,Z3ENVoff	; HL is now the address of the word
	pop	de
	ld	(hl),e
	inc	hl
	ld	(hl),d		; Set it appropriately
	rst	0		; And exit.
	
	
SCBPB:	; System control block function parameter block.
	db	03bh
	db	0		; Get operation