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cc65/libsrc/cbm510/emd/cbm510-ram.s
Oliver Schmidt 2c975d3642 Create static drivers directly from source files.
Up to now static drivers were created via co65 from dynamic drivers. However there was an issue with that approach:

The dynamic drivers are "o65 simple files" which obligates that they start with the 'code' segment. However dynamic drivers need to start with the module header - which is written to. For dynamic drivers this isn't more than a conceptual issue because they are always contain a 'data' segment and may therefore only be loaded into writable memory.

However when dynamic drivers are converted to static drivers using co65 then that issue becomes a real problem as then the 'code' segment may end up in non-writable memory - and thus writing to the module header fails.

Instead of changing the way dynamic drivers work I opted to rather make static driver creation totally independent from dynamic drivers. This allows to place the module header in the 'data' segment (see 'module.mac').
2014-06-04 23:50:18 +02:00

329 lines
7.1 KiB
ArmAsm

;
; Extended memory driver for the CBM510 additional RAM banks. Driver works
; without problems when linked statically.
;
; Ullrich von Bassewitz, 2002-12-09, 2003-12-27
;
.include "zeropage.inc"
.include "em-kernel.inc"
.include "em-error.inc"
.include "cbm510.inc"
.macpack generic
.macpack module
; ------------------------------------------------------------------------
; Header. Includes jump table
module_header _cbm510_ram_emd
; Driver signature
.byte $65, $6d, $64 ; "emd"
.byte EMD_API_VERSION ; EM API version number
; Library reference
.addr $0000
; Jump table
.addr INSTALL
.addr UNINSTALL
.addr PAGECOUNT
.addr MAP
.addr USE
.addr COMMIT
.addr COPYFROM
.addr COPYTO
; ------------------------------------------------------------------------
; Constants
RAMBANK = 1
OFFS = 2
; ------------------------------------------------------------------------
; Data.
.bss
curpage: .res 1 ; Current page number
window: .res 256 ; Memory "window"
pagecount: .res 1 ; Number of available pages
.code
; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. If
; possible, check if the hardware is present and determine the amount of
; memory available.
; Must return an EM_ERR_xx code in a/x.
;
INSTALL:
lda #$FF
sta curpage ; Invalidate the current page
sta pagecount ; Assume all memory available
sec
jsr $FF99 ; MEMTOP
cmp #RAMBANK ; Top of memory in bank 2?
bne @L1 ; No: We can use all the memory
txa
sub #OFFS
tya
sbc #$00
sta pagecount
@L1: 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 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 #$00
@L1: .repeat 2
lda (ptr1),y
sta window,y
iny
.endrepeat
bne @L1
stx IndReg
; Return the memory window
lda #<window
ldx #>window ; Return the window address
rts
; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.
USE: sta curpage ; Remember the page
lda #<window
ldx #>window ; Return the window
rts
; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.
COMMIT: lda curpage ; Get the current page
cmp #$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: .repeat 2
lda window,y
sta (ptr1),y
iny
.endrepeat
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 (ptr3),y
tax
dey
lda (ptr3),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