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cc65/libsrc/c16/emd/c16-ram.s
Oliver Schmidt 619b215260 Added library reference em_libref to EMD interface.
Occasionally dynamically drivers suffer from not being to refer to
content in the C library. Therefore I added a mechanism to allow
a C library for a certian target to define a symbol that will be
handed over to dynamic drivers for that target. Then the drivers
can use their refernce to that symbol to access content in the C
library.
2013-06-01 00:11:31 +02:00

274 lines
6.8 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
; Library reference
.addr $0000
; Jump table
.addr INSTALL
.addr UNINSTALL
.addr PAGECOUNT
.addr MAP
.addr USE
.addr COMMIT
.addr COPYFROM
.addr 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