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cc65/libsrc/c16/c16-ram.s
uz 5c5d01d84a Moved most platform assembler includes into asminc, so they will be available
in the distribution. 
Added --forget-inc-paths to the command line of the assembler in the
Makefiles, because the assembler does now have builtin paths and will find
include files from an installation first.
Hopefully fixed any problems that arose from the two changes.


git-svn-id: svn://svn.cc65.org/cc65/trunk@4223 b7a2c559-68d2-44c3-8de9-860c34a00d81
2009-09-24 17:44:22 +00:00

270 lines
6.6 KiB
ArmAsm

;
; Extended memory driver for the C16 hidden RAM. Driver works without
; problems when statically linked.
;
; Ullrich von Bassewitz, 2003-12-15
;
.include "zeropage.inc"
.include "em-kernel.inc"
.include "em-error.inc"
.include "plus4.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 = $8000
; ------------------------------------------------------------------------
; Data.
.bss
pages: .res 1 ; Number of pages
curpage: .res 1 ; Current page number
window: .res 256 ; Memory "window"
.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:
; Determine how much memory is available. We will use all memory above
; $8000 up to MEMTOP
sec
jsr $FF99 ; MEMTOP: Get top memory into Y/X
tya
sub #>BASE ; Low 32 K are used
bcc nomem
beq nomem ; Offering zero pages is a bad idea
sta pages
ldx #$FF
stx curpage ; Invalidate the current page
inx ; X = 0
txa ; A = X = EM_ERR_OK
rts
nomem: ldx #>EM_ERR_NO_DEVICE
lda #<EM_ERR_NO_DEVICE
; 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 #$00 ; 128 pages max
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
add #>BASE
sta ptr1+1
ldy #$00
sty ptr1
lda #<window
sta ptr2
lda #>window
sta ptr2+1
; Transfer one page
jsr transfer ; Transfer one page
; 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
bmi done ; Jump if no page mapped
add #>BASE
sta ptr2+1
ldy #$00
sty ptr2
lda #<window
sta ptr1
lda #>window
sta ptr1+1
; Transfer one page. Y must be zero on entry. Because we bank out the
; kernal, we will run the routine with interrupts disabled but leave
; short breath times. Unroll the following loop to make it somewhat faster.
transfer:
sei
sta ENABLE_RAM
.repeat 8
lda (ptr1),y
sta (ptr2),y
iny
.endrepeat
sta ENABLE_ROM
cli
bne transfer
; 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:
sta ptr3
stx ptr3+1 ; Save the passed em_copy pointer
ldy #EM_COPY::OFFS
lda (ptr3),y
sta ptr1
ldy #EM_COPY::PAGE
lda (ptr3),y
add #>BASE
sta ptr1+1 ; From
ldy #EM_COPY::BUF
lda (ptr3),y
sta ptr2
iny
lda (ptr3),y
sta ptr2+1 ; To
common: ldy #EM_COPY::COUNT+1
lda (ptr3),y ; Get number of pages
beq @L2 ; Skip if no full pages
sta tmp1
; Copy full pages allowing interrupts after each page copied
ldy #$00
@L1: jsr transfer
inc ptr1+1
inc ptr2+1
dec tmp1
bne @L1
; Copy the remainder of the page
@L2: ldy #EM_COPY::COUNT
lda (ptr3),y ; Get bytes in last page
beq @L4
tax
sei ; Disable ints
sta ENABLE_RAM ; Bank out the ROM
; Transfer the bytes in the last page
ldy #$00
@L3: lda (ptr1),y
sta (ptr2),y
iny
dex
bne @L3
; Restore the old memory configuration, allow interrupts
sta ENABLE_ROM
cli
; Done
@L4: 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: sta ptr3
stx ptr3+1 ; Save the passed em_copy pointer
ldy #EM_COPY::OFFS
lda (ptr3),y
sta ptr2
ldy #EM_COPY::PAGE
lda (ptr3),y
add #>BASE
sta ptr2+1 ; To
ldy #EM_COPY::BUF
lda (ptr3),y
sta ptr1
iny
lda (ptr3),y
sta ptr1+1 ; From
jmp common