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cc65/libsrc/cbm510/cbm510-ram.s
cuz b3ed17f575 Added EMD drivers for the Commodore B machines.
Note: These drivers are currently untested because I didn't realize that
using the drivers would need file routines, which are not available right
now. So in fact the drivers are not only untested, they are also unusable
on the target platforms, because they cannot be loaded.


git-svn-id: svn://svn.cc65.org/cc65/trunk@1732 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-12-10 10:30:01 +00:00

320 lines
6.7 KiB
ArmAsm

;
; Extended memory driver for the CBM510 additional RAM banks
;
; Ullrich von Bassewitz, 2002-12-09 !!! UNTESTED !!!
;
.include "zeropage.inc"
.include "em-kernel.inc"
.include "em-error.inc"
.include "cbm510.inc"
.macpack generic
; ------------------------------------------------------------------------
; Header. Includes jump table
.segment "JUMPTABLE"
; Driver signature
.byte $65, $6d, $64 ; "emd"
.byte $00 ; EM API version number
; Jump table.
.word INSTALL
.word DEINSTALL
.word PAGECOUNT
.word MAP
.word USE
.word COMMIT
.word COPYFROM
.word COPYTO
; ------------------------------------------------------------------------
; Constants
RAMBANK = 2
OFFS = 2
; ------------------------------------------------------------------------
; Data.
.data
curpage: .byte $FF ; Current page number (invalid)
.bss
window: .res 256 ; Memory "window"
pagecount: .res 1 ; Number of available pages
.code
; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. If
; possible, check if the hardware is present and determine the amount of
; memory available.
; Must return an EM_ERR_xx code in a/x.
;
INSTALL:
lda #$FF
ldx UsrMemTop+2
cpx #RAMBANK ; Top of memory in bank 2?
bne @L1 ; No: We can use all the memory
clc
adc UsrMemTop+1
@L1: sta pagecount
lda #<EM_ERR_OK
ldx #>EM_ERR_OK
rts
; ------------------------------------------------------------------------
; DEINSTALL routine. Is called before the driver is removed from memory.
; Can do cleanup or whatever. Must not return anything.
;
DEINSTALL:
rts
; ------------------------------------------------------------------------
; PAGECOUNT: Return the total number of available pages in a/x.
;
PAGECOUNT:
lda pagecount
ldx #0
rts
; ------------------------------------------------------------------------
; MAP: Map the page in a/x into memory and return a pointer to the page in
; a/x. The contents of the currently mapped page (if any) may be discarded
; by the driver.
;
MAP: sta curpage ; Remember the new page
sta ptr1+1
lda #OFFS
sta ptr1
; Transfer one page
ldx IndReg
lda #RAMBANK
sta IndReg
ldy #$00
@L1: lda (ptr1),y
sta window,y
iny
lda (ptr1),y
sta window,y
iny
bne @L1
stx IndReg
; Return the memory window
lda #<window
ldx #>window ; Return the window address
rts
; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.
USE: sta curpage ; Remember the page
lda #<window
ldx #>window ; Return the window
rts
; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.
COMMIT: lda curpage ; Get the current page
cmp #$FF
beq done ; Jump if no page mapped
sta ptr1+1
lda #OFFS
sta ptr1
; Transfer one page
ldx IndReg
lda #RAMBANK
sta IndReg
ldy #$00
@L1: lda window,y
sta (ptr1),y
iny
lda window,y
sta (ptr1),y
iny
bne @L1
stx IndReg
; Done
done: rts
; ------------------------------------------------------------------------
; COPYFROM: Copy from extended into linear memory. A pointer to a structure
; describing the request is passed in a/x.
; The function must not return anything.
;
COPYFROM:
jsr setup
; Setup the buffer address in this bank.
sta copyfrom_buf
stx copyfrom_buf+1
; Check if we must copy full pages
ldx ptr2+1
beq @L2
; Copy full pages
ldx #$00
@L1: jsr copyfrom
inc ptr1+1
inc copyfrom_buf+1
@L2: dec ptr2+1
bne @L1
; Copy the remaining page
ldx ptr2
beq @L3
jsr copyfrom
; Restore the indirect segment
@L3: lda ExecReg
sta IndReg
; Done
rts
; ------------------------------------------------------------------------
; COPYTO: Copy from linear into extended memory. A pointer to a structure
; describing the request is passed in a/x.
; The function must not return anything.
;
COPYTO: jsr setup
; Setup the buffer address in this bank.
sta copyto_buf
stx copyto_buf+1
; Check if we must copy full pages
ldx ptr2+1
beq @L2
; Copy full pages
ldx #$00
@L1: jsr copyto
inc ptr1+1
inc copyto_buf+1
@L2: dec ptr2+1
bne @L1
; Copy the remaining page
ldx ptr2
beq @L3
jsr copyto
; Restore the indirect segment
@L3: lda ExecReg
sta IndReg
; Done
rts
; ------------------------------------------------------------------------
; setup: Helper function for COPYFROM and COPYTO, will setup parameters.
;
setup: sta ptr3
stx ptr3+1 ; Save the passed em_copy pointer
ldy #EM_COPY_OFFS
lda (ptr3),y
add #OFFS
sta ptr1
ldy #EM_COPY_PAGE
lda (ptr3),y
adc #$00
sta ptr1+1
ldy #EM_COPY_COUNT
lda (ptr3),y
sta ptr2
iny
lda (ptr3),y
sta ptr2+1 ; Get count into ptr2
ldy #EM_COPY_BUF+1
lda (ptr1),y
tax
dey
lda (ptr1),y ; Get the buffer pointer into a/x
ldy #RAMBANK
sty IndReg
ldy #$00
rts
; ------------------------------------------------------------------------
; copyfrom
.data
copyfrom:
lda (ptr1),y
copyfrom_buf = * + 1
sta $0000,y
iny
dex
bne copyfrom
rts
; ------------------------------------------------------------------------
; copyto
.data
copyto:
copyto_buf = * + 1
lda $0000,y
sta (ptr1),y
iny
dex
bne copyto
rts