;
; Extended memory driver for the GEORAM cartridge. Driver works without
; problems when statically linked.
;
; Ullrich von Bassewitz, 2002-11-29
;
; GEORAM page size checking routine by
; Marco van den Heuvel, 2010-01-21
;
.include "zeropage.inc"
.include "em-kernel.inc"
.include "em-error.inc"
.macpack generic
; ------------------------------------------------------------------------
; Header. Includes jump table
.segment "JUMPTABLE"
; Driver signature
.byte $65, $6d, $64 ; "emd"
.byte EMD_API_VERSION ; EM API version number
; Jump table.
.word INSTALL
.word UNINSTALL
.word PAGECOUNT
.word MAP
.word USE
.word COMMIT
.word COPYFROM
.word COPYTO
; ------------------------------------------------------------------------
; Constants
GR_WINDOW = $DE00 ; Address of GEORAM window
GR_PAGE_LO = $DFFE ; Page register low
GR_PAGE_HI = $DFFF ; Page register high
; ------------------------------------------------------------------------
; Data.
.data
pagecount: .res 2 ; 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:
ldx GR_WINDOW
cpx GR_WINDOW
bne @notpresent
inc GR_WINDOW
cpx GR_WINDOW
beq @notpresent
lda #4
jsr check
cpy GR_WINDOW
beq @has64k
lda #8
jsr check
cpy GR_WINDOW
beq @has128k
lda #16
jsr check
cpy GR_WINDOW
beq @has256k
lda #32
jsr check
cpy GR_WINDOW
beq @has512k
lda #64
jsr check
cpy GR_WINDOW
beq @has1024k
lda #128
jsr check
cpy GR_WINDOW
beq @has2048k
ldx #>16384
bne @setok
@has64k:
ldx #>256
bne @setok
@has128k:
ldx #>512
bne @setok
@has256k:
ldx #>1024
bne @setok
@has512k:
ldx #>2048
bne @setok
@has1024k:
ldx #>4096
bne @setok
@has2048k:
ldx #>8192
bne @setok
@notpresent:
lda #<EM_ERR_NO_DEVICE
ldx #>EM_ERR_NO_DEVICE
rts
@setok:
lda #0
sta pagecount
stx pagecount+1
lda #<EM_ERR_OK
ldx #>EM_ERR_OK
rts
check:
ldx #0
stx GR_PAGE_LO
stx GR_PAGE_HI
ldy GR_WINDOW
iny
sta GR_PAGE_HI
sty GR_WINDOW
ldx #0
stx GR_PAGE_HI
; rts ; Run into UNINSTALL instead
; ------------------------------------------------------------------------
; UNINSTALL routine. Is called before the driver is removed from memory.
; Can do cleanup or whatever. Must not return anything.
;
UNINSTALL:
rts
; ------------------------------------------------------------------------
; PAGECOUNT: Return the total number of available pages in a/x.
;
PAGECOUNT:
lda pagecount
ldx pagecount+1
rts
; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.
; The GeoRAM cartridge does not copy but actually map the window, so USE is
; identical to MAP.
USE = MAP
; ------------------------------------------------------------------------
; 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 tmp1
txa
asl tmp1
rol a
asl tmp1
rol a
sta GR_PAGE_HI
lda tmp1
lsr a
lsr a
sta GR_PAGE_LO
lda #<GR_WINDOW
ldx #>GR_WINDOW
; Use the RTS from COMMIT below to save a precious byte of storage
; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.
COMMIT: 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 is:
;
; - ptr1 contains the struct pointer
; - ptr2 contains the linear memory buffer
; - ptr3 contains -(count-1)
; - tmp1 contains the low page register value
; - tmp2 contains the high page register value
; - X contains the page offset
; - Y contains zero
jmp @L5
@L1: lda GR_WINDOW,x
sta (ptr2),y
iny
bne @L2
inc ptr2+1
@L2: inx
beq @L4
; Bump count and repeat
@L3: inc ptr3
bne @L1
inc ptr3+1
bne @L1
rts
; Bump page register
@L4: inc tmp1 ; Bump low page register
bit tmp1 ; Check for overflow in bit 6
bvc @L6 ; Jump if no overflow
inc tmp2
@L5: lda tmp2
sta GR_PAGE_HI
@L6: lda tmp1
sta GR_PAGE_LO
jmp @L3
; ------------------------------------------------------------------------
; 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 is:
;
; - ptr1 contains the struct pointer
; - ptr2 contains the linear memory buffer
; - ptr3 contains -(count-1)
; - tmp1 contains the low page register value
; - tmp2 contains the high page register value
; - X contains the page offset
; - Y contains zero
jmp @L5
@L1: lda (ptr2),y
sta GR_WINDOW,x
iny
bne @L2
inc ptr2+1
@L2: inx
beq @L4
; Bump count and repeat
@L3: inc ptr3
bne @L1
inc ptr3+1
bne @L1
rts
; Bump page register
@L4: inc tmp1 ; Bump low page register
bit tmp1 ; Check for overflow in bit 6
bvc @L6 ; Jump if no overflow
inc tmp2
@L5: lda tmp2
sta GR_PAGE_HI
@L6: lda tmp1
sta GR_PAGE_LO
jmp @L3
; ------------------------------------------------------------------------
; Helper function for COPYFROM and COPYTO: Store the pointer to the request
; structure and prepare data for the copy
setup: sta ptr1
stx ptr1+1 ; Save passed pointer
; Get the page number from the struct and adjust it so that it may be used
; with the hardware. That is: lower 6 bits in tmp1, high bits in tmp2.
ldy #EM_COPY::PAGE+1
lda (ptr1),y
sta tmp2
dey
lda (ptr1),y
asl a
rol tmp2
asl a
rol tmp2
lsr a
lsr a
sta tmp1
; Get the buffer pointer into ptr2
ldy #EM_COPY::BUF
lda (ptr1),y
sta ptr2
iny
lda (ptr1),y
sta ptr2+1
; Get the count, calculate -(count-1) and store it into ptr3
ldy #EM_COPY::COUNT
lda (ptr1),y
eor #$FF
sta ptr3
iny
lda (ptr1),y
eor #$FF
sta ptr3+1
; Get the page offset into X and clear Y
ldy #EM_COPY::OFFS
lda (ptr1),y
tax
ldy #$00
; Done
rts