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cc65/libsrc/c64/c64-c256k.s

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;
; Extended memory driver for the C256K memory expansion
; Marco van den Heuvel, 2010-01-27
;
.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
BASE = $4000
PAGES = 3 * 256
TARGETLOC = $200 ; Target location for copy/check code
PIA = $DFC0
; ------------------------------------------------------------------------
; Data.
.data
; This function is used to copy code from and to the extended memory
.proc copy
template:
.org ::TARGETLOC ; Assemble for target location
entry:
stx PIA
stashop = $91 ; 'sta' opcode
operation := * ; Location and opcode is patched at runtime
address := *+1
lda ($00),y
ldx #$dc
stx PIA
rts
.reloc
.endproc
; This function is used to check for the existence of the extended memory
.proc check
template:
.org ::TARGETLOC
entry:
ldy #$00 ; Assume hardware not present
lda #$fc
sta PIA
lda $01
tax
and #$f8
sta $01
lda $4000
cmp $c000
bne done ; Jump if not found
inc $c000
cmp $4000
beq done ; Jump if not found
; Hardware is present
iny
done: stx $01
ldx #$dc
stx PIA
rts
.reloc
.endproc
.bss
curpage: .res 2 ; Current page number
curbank: .res 1 ; Current bank
window: .res 256 ; Memory "window"
; Since the functions above are copied to $200, the current contents of this
; memory area must be saved into backup storage. Allocate enough space.
backup: .res .max (.sizeof (copy), .sizeof (check))
.code
; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. If
; possible, check if the hardware is present and determine the amount of
; memory available.
; Must return an EM_ERR_xx code in a/x.
;
INSTALL:
lda PIA+1 ; Select Peripheral Registers
ora #4
sta PIA+1
tax
lda PIA+3
ora #4
sta PIA+3
tay
lda #$DC ; Set the default memory bank data
sta PIA
lda #$FE
sta PIA+2
txa ; Select Data Direction Registers
and #$FB
sta PIA+1
tya
and #$FB
sta PIA+3
lda #$FF ; Set the ports to output
sta PIA
sta PIA+2
txa
and #$C7
ora #$30 ; Set CA1 and
sta PIA+1 ; select Peripheral Registers
sty PIA+3
jsr backup_and_setup_check_routine
jsr check::entry
cli
ldx #.sizeof (check) - 1
jsr restore_data
cpy #$01
beq @present
lda #<EM_ERR_NO_DEVICE
ldx #>EM_ERR_NO_DEVICE
rts
@present:
lda #<EM_ERR_OK
ldx #>EM_ERR_OK
; 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 #<PAGES
ldx #>PAGES
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:
sei
sta curpage ; Remember the new page
stx curpage+1
jsr adjust_page_and_bank
stx curbank
clc
adc #>BASE
sta ptr1+1
ldy #0
sty ptr1
jsr backup_and_setup_copy_routine
ldx #<ptr1
stx copy::address
@L1:
ldx curbank
jsr copy::entry
ldx ptr1
sta window,x
inc ptr1
bne @L1
; Return the memory window
jsr restore_copy_routine
lda #<window
ldx #>window ; Return the window address
cli
rts
; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.
USE: sta curpage ; Remember the page
stx curpage+1
lda #<window
ldx #>window ; Return the window
rts
; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.
COMMIT:
sei
lda curpage ; Get the current page
ldx curpage+1
jsr adjust_page_and_bank
stx curbank
clc
adc #>BASE
sta ptr1+1
ldy #0
sty ptr1
jsr backup_and_setup_copy_routine
ldx #<ptr1
stx copy::address
ldx #<copy::stashop
stx copy::operation
@L1:
ldx ptr1
lda window,x
ldx curbank
jsr copy::entry
inc ptr1
bne @L1
; Return the memory window
jsr restore_copy_routine
done:
cli
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:
sei
jsr setup
jsr backup_and_setup_copy_routine
; Setup is:
;
; - ptr1 contains the struct pointer
; - ptr2 contains the linear memory buffer
; - ptr3 contains -(count-1)
; - ptr4 contains the page memory buffer plus offset
; - tmp1 contains zero (to be used for linear memory buffer offset)
; - tmp2 contains the bank value
lda #<ptr4
sta copy::address
jmp @L3
@L1:
ldx tmp2
ldy #0
jsr copy::entry
ldy tmp1
sta (ptr2),y
inc tmp1
bne @L2
inc ptr2+1
@L2:
inc ptr4
beq @L4
; Bump count and repeat
@L3:
inc ptr3
bne @L1
inc ptr3+1
bne @L1
jsr restore_copy_routine
cli
rts
; Bump page register
@L4:
inc ptr4+1
lda ptr4+1
cmp #$80
bne @L3
lda #>BASE
sta ptr4+1
lda tmp2
clc
adc #$10
sta tmp2
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:
sei
jsr setup
jsr backup_and_setup_copy_routine
; Setup is:
;
; - ptr1 contains the struct pointer
; - ptr2 contains the linear memory buffer
; - ptr3 contains -(count-1)
; - ptr4 contains the page memory buffer plus offset
; - tmp1 contains zero (to be used for linear memory buffer offset)
; - tmp2 contains the bank value
lda #<ptr4
sta copy::address
lda #<copy::stashop
sta copy::operation
jmp @L3
@L1:
ldy tmp1
lda (ptr2),y
ldx tmp2
ldy #0
jsr copy::entry
inc tmp1
bne @L2
inc ptr2+1
@L2:
inc ptr4
beq @L4
; Bump count and repeat
@L3:
inc ptr3
bne @L1
inc ptr3+1
bne @L1
jsr restore_copy_routine
cli
rts
; Bump page register
@L4:
inc ptr4+1
lda ptr4+1
cmp #$80
bne @L3
lda #>BASE
sta ptr4+1
lda tmp2
clc
adc #$10
sta tmp2
jmp @L3
; ------------------------------------------------------------------------
; Helper function for COPYFROM and COPYTO: Store the pointer to the request
; structure and prepare data for the copy
setup:
sta ptr1
stx ptr1+1 ; Save passed pointer
; Get the page number from the struct and adjust it so that it may be used
; with the hardware. That is: ptr4 has the page address and page offset
; tmp2 will hold the bank value
ldy #EM_COPY::PAGE+1
lda (ptr1),y
tax
ldy #EM_COPY::PAGE
lda (ptr1),y
jsr adjust_page_and_bank
clc
adc #>BASE
sta ptr4+1
stx tmp2
; Get the buffer pointer into ptr2
ldy #EM_COPY::BUF
lda (ptr1),y
sta ptr2
iny
lda (ptr1),y
sta ptr2+1
; Get the count, calculate -(count-1) and store it into ptr3
ldy #EM_COPY::COUNT
lda (ptr1),y
eor #$FF
sta ptr3
iny
lda (ptr1),y
eor #$FF
sta ptr3+1
; Get the page offset into ptr4 and clear tmp1
ldy #EM_COPY::OFFS
lda (ptr1),y
sta ptr4
lda #0
sta tmp1
; Done
rts
; Helper routines for copying to and from the +256k ram
backup_and_setup_copy_routine:
ldx #.sizeof (copy) - 1
@L1:
lda copy::entry,x
sta backup,x
lda copy::template,x
sta copy::entry,x
dex
bpl @L1
rts
backup_and_setup_check_routine:
ldx #.sizeof (check) - 1
@L1:
lda check::entry,x
sta backup,x
lda check::template,x
sta check::entry,x
dex
bpl @L1
rts
restore_copy_routine:
ldx #.sizeof (copy) - 1
restore_data:
lda backup,x
sta TARGETLOC,x
dex
bpl restore_data
rts
; Helper routine to correct for the bank and page
adjust_page_and_bank:
sta tmp4
lda #$0C
sta tmp3
lda tmp4
and #$c0
lsr
lsr
ora tmp3
sta tmp3
txa
asl
asl
asl
asl
asl
asl
ora tmp3
tax
lda tmp4
and #$3f
rts