;
; Extended memory driver for the Commodore REU. Driver works without
; problems when statically linked.
;
; Ullrich von Bassewitz, 2002-11-29
;
.include "zeropage.inc"
.include "em-kernel.inc"
.include "em-error.inc"
.include "c128.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
REU_STATUS = $DF00 ; Status register
REU_COMMAND = $DF01 ; Command register
REU_C64ADDR = $DF02 ; C64 base address register
REU_REUADDR = $DF04 ; REU base address register
REU_COUNT = $DF07 ; Transfer count register
REU_IRQMASK = $DF09 ; IRQ mask register
REU_CONTROL = $DF0A ; Control register
REU_TRIGGER = $FF00 ; REU command trigger
OP_COPYFROM = $ED
OP_COPYTO = $EC
; ------------------------------------------------------------------------
; Data.
.bss
pagecount: .res 2 ; Number of pages available
curpage: .res 2 ; Current page number
window: .res 256 ; Memory "window"
reu_params: .word $0000 ; Host address, lo, hi
.word $0000 ; Exp address, lo, hi
.byte $00 ; Expansion bank no.
.word $0000 ; # bytes to move, lo, hi
.byte $00 ; Interrupt mask reg.
.byte $00 ; Adress control reg.
.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 #$00 ; High byte of return code
lda #$55
sta REU_REUADDR
cmp REU_REUADDR ; Check for presence of REU
bne nodevice
asl a ; A = $AA
sta REU_REUADDR
cmp REU_REUADDR ; Check for presence of REU
bne nodevice
ldy #>(128*4) ; Assume 128KB
lda REU_STATUS
and #$10 ; Check size bit
beq @L1
ldy #>(256*4) ; 256KB when size bit is set
@L1: sty pagecount+1
ldy #$FF
sty curpage
sty curpage+1 ; Invalidate the current page
txa ; X = A = EM_ERR_OK
rts
; No REU found
nodevice:
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 pagecount
ldx pagecount+1
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
stx curpage+1 ; Remember the new page
ldy #OP_COPYFROM
jsr common ; Copy the window
lda #<window
ldx #>window ; Return the window address
done: rts
; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.
USE: sta curpage
stx curpage+1 ; Remember the page
lda #<window
ldx #>window ; Return the window
rts
; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.
COMMIT: lda curpage
ldx curpage+1 ; Do we have a page mapped?
bmi done ; Jump if no page mapped
ldy #OP_COPYTO
common: sty tmp1
ldy #<window
sty REU_C64ADDR
ldy #>window
sty REU_C64ADDR+1
ldy #0
sty REU_REUADDR+0
sta REU_REUADDR+1
stx REU_REUADDR+2
sty REU_COUNT+0
ldy #1
sty REU_COUNT+1 ; Move 256 bytes
bne transfer1 ; Transfer 256 bytes into REU
; ------------------------------------------------------------------------
; 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:
ldy #OP_COPYFROM
.byte $2C
; ------------------------------------------------------------------------
; 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:
ldy #OP_COPYTO
sty tmp1
; Remember the passed pointer
sta ptr1
stx ptr1+1 ; Save the pointer
; The structure passed to the functions has the same layout as the registers
; of the Commodore REU, so register programming is easy.
ldy #7-1
@L1: lda (ptr1),y
sta REU_C64ADDR,y
dey
bpl @L1
; Invalidate the page in the memory window
sty curpage+1 ; Y = $FF
; Reload the REU command and start the transfer
transfer1:
ldy tmp1
; Transfer subroutine for the REU. Expects command in Y.
transfer:
sty REU_COMMAND ; Issue command
ldy MMU_CR ; Save the current MMU settings
lda #MMU_CFG_RAM0 ;
sei ;
sta MMU_CR ; Enable RAM in bank #0
lda REU_TRIGGER ; Don't change $FF00
sta REU_TRIGGER ; Start the transfer...
sty MMU_CR ; Restore the old configuration
cli
rts