page	255
	.z80


	global mmuinit
	global bnk2log,bnk2phy,hwl2phy

	include config.inc
	include	z180reg.inc


;----------------------------------------------------------------------
; Memory Map:
;
;	Common	CAStart ...     0FFFF
;	Bank 0	  00000 ... CAStart-1
;	Bank 1    10000 ...
;	Bank 2
;
;----------------------------------------------------------------------

	cseg

mmuinit:
	ld	a,USR$CBAR
	out0	(cbar),a
	ret

;--------------------------------------------------------------------
; Return the BBR value for the given bank number
;
; in  a: Bank number
; out a: bbr value

bnk2log:
	or	a		;
	ret	z		; Bank 0 is at physical address 0

	dec	a
	push	bc		;
	ld	b,a		;
	ld	c,CA		;
	mlt	bc		; bank size * bank number
	ld	a,c		;
	add	a,10h		; add bank0 + common
	pop	bc		;
	ret			;

;--------------------------------------------------------------

;in  hl: Log. Address
;     a: Bank number
;
;out ahl: Phys. (linear) Address


bnk2phy:
	push	bc
	ld	c,a
	ld	a,h
	and	a,0f0h
	cp	CA*16
	ld	a,c
	pop	bc

	jr	c,b2p_banked
	xor	a		; address is in common
	jr	b2b_cont	;    base is 0
b2p_banked:
	call	bnk2log		; get address base
b2b_cont:

	; fall thru

;--------------------------------------------------------------
;
; hl: Log. Address
;  a: Bank base (bbr)
;
;	     2           0       0
;	     0   6       8       0
; hl	          hhhhhhhhllllllll
;  a	+     bbbbbbbb
;
; OP: ahl = (a<<12) + (h<<8) + l
;
;out ahl: Phys. (linear) Address

log2phy:
	push	bc		;
l2p_i:
	ld	c,a		;
	ld	b,16		;
	mlt	bc		; bc = a<<4
	ld	a,c		;
	add	a,h		;
	ld	h,a		;
	ld	a,b		;
	adc	a,0		;
	pop	bc		;
	ret			;

;--------------------------------------------------------------
;
; de: Log. Address
;
;
; OP: ahl = (bankbase<<12) + (d<<8) + e
;
;out ahl: Phys. (linear) Address


hwl2phy:
	push	bc		;
	in0	c,(cbar)	;
	ld	a,h		;
	or	00fh		; log. addr in common1?
	cp	c
	jr	c,hlp_1

	in0	a,(cbr)		; yes, cbr is address base
	jr	hl2p_x
hlp_1:
	ld	b,16		; log. address in baked area?
	mlt	bc
	ld	a,h
	cp	c
	jr	c,hlp_2
	in0	a,(bbr)		; yes, bbr is address base
	jr	hl2p_x
hlp_2:
	xor	a		; common1
hl2p_x:
	jr	nz,l2p_i

	pop	bc		; bank part is 0, no translation
	ret			;


;--------------------------------------------------------------
; Trampoline for routines in banked ram.
; Switch stack pointer to "system" stack in top ram
; Save cbar
;
	extrn	bs$stack

	cseg	; common!

	public	_b0call
_b0call:
	push	af
	in0	a,(bbr)
	jr	nz,b0c_doit
	pop	af

	ex	(sp),hl			;16
	push	de
	ld	e,(hl)
	inc	hl
	ld	d,(hl)
	inc	hl
	ld	(b0c_fast_go),de
	pop	de
	ex	(sp),hl			;16
b0c_fast_go equ	$+1
	jp	0

b0c_doit:
	ld	(b0_save_hl),hl
	ld	(b0_save_de),de
	pop	hl
	ld	(b0_save_af),hl

	pop	de			;get ptr to 'function address' in de
	ld	hl,2
	add	hl,de
	push	hl			;put return address on stack

   if 0 ; link80

	ld	hl,0
	add	hl,sp			;
	ld	a,h
	cp	high (bs$stack-bs$stack$size) ;link80 can't process this
	jr	nc,$ + 5		;skip if stack allready in common bios ram

   else

	ld	hl,bs$stack-bs$stack$size
	ld	a,h
	dec	a
	ld	hl,0
	add	hl,sp			;
	cp	h
	jr	c,$ + 5			;skip if stack allready in common bios ram
   endif
	ld	sp,bs$stack		;

	push	hl			;save	user stack pointer

	in0	h,(bbr)			;
	push	hl			;
	ld	hl,b0c_ret
	push	hl
	xor	a
	out0	(bbr),a			;
	ex	de,hl			;ptr
	ld	e,(hl)			;get 'function address'
	inc	hl			;
	ld	d,(hl)			;
	push	de			;put on (switched) stack

	ld	hl,(b0_save_af)		;get back users registers
	push	hl
	pop	af
	ld	de,(b0_save_de)
	ld	hl,(b0_save_hl)
	ret				;go to function
b0c_ret:
	ld	(b0_save_hl),hl

	pop	hl			;
	out0	(bbr),h			;
	pop	hl			;
	ld	sp,hl			;
	ld	hl,(b0_save_hl)
	ret				;


b0_save_hl: dw	0
b0_save_de: dw	0
b0_save_af: dw	0



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

  if 0

;--------------------------------------------------------------------
; Return the BBR value for the given bank number

bnk2bbr:
	or	a		; 4
	ret	z		; 5/10 | 11		14

	push	bc		;11 | 11
	ld	b,a		; 4
	ld	c,CA		; 6
	mlt	bc		;17			    >45
	ld	a,c		; 4
	add	a,10h		; 6
	pop	bc		; 9 | 10
	ret			; 9 | 10		76

	push	ix		;2 / 14 | 15
	ld	ix,bnktbl	;4 / 12 | 14
	ld	($+3+2),a	;3 / 15 | 19
	ld	a,(ix+0)	;3 / 14 | 19
	pop	ix		;2 / 12 | 14
	ret			;1 /  9 | 10		15 / 76|91

	push	hl		;1 / 11 | 11
	ld	hl,bnktbl	;3 /  9 | 10
	add	a,l		;1 /  4 | 4
	ld	l,a		;1 /  4 | 4
	ld	a,0		;1 /  6 | 7
	adc	a,h		;1 /  4 | 4
	ld	h,a		;1 /  4 | 4
	ld	a,(hl)		;1 /  6 | 7
	pop	hl		;1 /  9 | 10
	ret			;1 /  9 | 10		12 / 66|71

	push	hl		;1 / 11 | 11
	add	a,low bnktbl	;2 /  6 | 7
	ld	l,a		;1 /  4 | 4
	ld	a,0		;1 /  6 | 7
	adc	a,high bnktbl	;2 /  6 | 7
	ld	h,a		;1 /  4 | 4
	ld	a,(hl)		;1 /  6 | 7
	pop	hl		;1 /  9 | 10
	ret			;1 /  9 | 10		11 / 61|67

  endif


	end