2 ; Extended memory driver for the Commodore REU. Driver works without
3 ; problems when statically linked.
5 ; Ullrich von Bassewitz, 2002-11-29
8 .include "zeropage.inc"
10 .include "em-kernel.inc"
11 .include "em-error.inc"
17 ; ------------------------------------------------------------------------
18 ; Header. Includes jump table
24 .byte $65, $6d, $64 ; "emd"
25 .byte EMD_API_VERSION ; EM API version number
42 ; ------------------------------------------------------------------------
45 REU_STATUS = $DF00 ; Status register
46 REU_COMMAND = $DF01 ; Command register
47 REU_C64ADDR = $DF02 ; C64 base address register
48 REU_REUADDR = $DF04 ; REU base address register
49 REU_COUNT = $DF07 ; Transfer count register
50 REU_IRQMASK = $DF09 ; IRQ mask register
51 REU_CONTROL = $DF0A ; Control register
52 REU_TRIGGER = $FF00 ; REU command trigger
58 ; ------------------------------------------------------------------------
62 pagecount: .res 2 ; Number of pages available
63 curpage: .res 2 ; Current page number
65 window: .res 256 ; Memory "window"
67 reu_params: .word $0000 ; Host address, lo, hi
68 .word $0000 ; Exp address, lo, hi
69 .byte $00 ; Expansion bank no.
70 .word $0000 ; # bytes to move, lo, hi
71 .byte $00 ; Interrupt mask reg.
72 .byte $00 ; Adress control reg.
76 ; ------------------------------------------------------------------------
77 ; INSTALL routine. Is called after the driver is loaded into memory. If
78 ; possible, check if the hardware is present and determine the amount of
80 ; Must return an EM_ERR_xx code in a/x.
84 ldx #$00 ; High byte of return code
87 cmp REU_REUADDR ; Check for presence of REU
91 cmp REU_REUADDR ; Check for presence of REU
94 ldy #>(128*4) ; Assume 128KB
96 and #$10 ; Check size bit
98 ldy #>(256*4) ; 256KB when size bit is set
103 sty curpage+1 ; Invalidate the current page
104 txa ; X = A = EM_ERR_OK
110 lda #EM_ERR_NO_DEVICE
111 ; rts ; Run into UNINSTALL instead
113 ; ------------------------------------------------------------------------
114 ; UNINSTALL routine. Is called before the driver is removed from memory.
115 ; Can do cleanup or whatever. Must not return anything.
122 ; ------------------------------------------------------------------------
123 ; PAGECOUNT: Return the total number of available pages in a/x.
131 ; ------------------------------------------------------------------------
132 ; MAP: Map the page in a/x into memory and return a pointer to the page in
133 ; a/x. The contents of the currently mapped page (if any) may be discarded
138 stx curpage+1 ; Remember the new page
141 jsr common ; Copy the window
144 ldx #>window ; Return the window address
147 ; ------------------------------------------------------------------------
148 ; USE: Tell the driver that the window is now associated with a given page.
151 stx curpage+1 ; Remember the page
153 ldx #>window ; Return the window
156 ; ------------------------------------------------------------------------
157 ; COMMIT: Commit changes in the memory window to extended storage.
160 ldx curpage+1 ; Do we have a page mapped?
161 bmi done ; Jump if no page mapped
178 sty REU_COUNT+1 ; Move 256 bytes
179 bne transfer1 ; Transfer 256 bytes into REU
181 ; ------------------------------------------------------------------------
182 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
183 ; describing the request is passed in a/x.
184 ; The function must not return anything.
191 ; ------------------------------------------------------------------------
192 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
193 ; describing the request is passed in a/x.
194 ; The function must not return anything.
201 ; Remember the passed pointer
204 stx ptr1+1 ; Save the pointer
206 ; The structure passed to the functions has the same layout as the registers
207 ; of the Commodore REU, so register programming is easy.
215 ; Invalidate the page in the memory window
217 sty curpage+1 ; Y = $FF
219 ; Reload the REU command and start the transfer
224 ; Transfer subroutine for the REU. Expects command in Y.
227 sty REU_COMMAND ; Issue command
229 ldy $01 ; Save the value of the c64 control port...
231 and #$F8 ; Disable ROMs and I/O.
234 lda REU_TRIGGER ; Don't change $FF00
235 sta REU_TRIGGER ; Start the transfer...
237 sty $01 ; Restore the old configuration