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"
18 ; ------------------------------------------------------------------------
19 ; Header. Includes jump table
21 module_header _c64_reu_emd
25 .byte $65, $6d, $64 ; "emd"
26 .byte EMD_API_VERSION ; EM API version number
43 ; ------------------------------------------------------------------------
46 REU_STATUS = $DF00 ; Status register
47 REU_COMMAND = $DF01 ; Command register
48 REU_C64ADDR = $DF02 ; C64 base address register
49 REU_REUADDR = $DF04 ; REU base address register
50 REU_COUNT = $DF07 ; Transfer count register
51 REU_IRQMASK = $DF09 ; IRQ mask register
52 REU_CONTROL = $DF0A ; Control register
53 REU_TRIGGER = $FF00 ; REU command trigger
59 ; ------------------------------------------------------------------------
63 pagecount: .res 2 ; Number of pages available
64 curpage: .res 2 ; Current page number
66 window: .res 256 ; Memory "window"
68 reu_params: .word $0000 ; Host address, lo, hi
69 .word $0000 ; Exp address, lo, hi
70 .byte $00 ; Expansion bank no.
71 .word $0000 ; # bytes to move, lo, hi
72 .byte $00 ; Interrupt mask reg.
73 .byte $00 ; Adress control reg.
77 ; ------------------------------------------------------------------------
78 ; INSTALL routine. Is called after the driver is loaded into memory. If
79 ; possible, check if the hardware is present and determine the amount of
81 ; Must return an EM_ERR_xx code in a/x.
85 ldx #$00 ; High byte of return code
88 cmp REU_REUADDR ; Check for presence of REU
92 cmp REU_REUADDR ; Check for presence of REU
95 ldy #>(128*4) ; Assume 128KB
97 and #$10 ; Check size bit
99 ldy #>(256*4) ; 256KB when size bit is set
104 sty curpage+1 ; Invalidate the current page
105 txa ; X = A = EM_ERR_OK
111 lda #EM_ERR_NO_DEVICE
112 ; rts ; Run into UNINSTALL instead
114 ; ------------------------------------------------------------------------
115 ; UNINSTALL routine. Is called before the driver is removed from memory.
116 ; Can do cleanup or whatever. Must not return anything.
123 ; ------------------------------------------------------------------------
124 ; PAGECOUNT: Return the total number of available pages in a/x.
132 ; ------------------------------------------------------------------------
133 ; MAP: Map the page in a/x into memory and return a pointer to the page in
134 ; a/x. The contents of the currently mapped page (if any) may be discarded
139 stx curpage+1 ; Remember the new page
142 jsr common ; Copy the window
145 ldx #>window ; Return the window address
148 ; ------------------------------------------------------------------------
149 ; USE: Tell the driver that the window is now associated with a given page.
152 stx curpage+1 ; Remember the page
154 ldx #>window ; Return the window
157 ; ------------------------------------------------------------------------
158 ; COMMIT: Commit changes in the memory window to extended storage.
161 ldx curpage+1 ; Do we have a page mapped?
162 bmi done ; Jump if no page mapped
179 sty REU_COUNT+1 ; Move 256 bytes
180 bne transfer1 ; Transfer 256 bytes into REU
182 ; ------------------------------------------------------------------------
183 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
184 ; describing the request is passed in a/x.
185 ; The function must not return anything.
192 ; ------------------------------------------------------------------------
193 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
194 ; describing the request is passed in a/x.
195 ; The function must not return anything.
202 ; Remember the passed pointer
205 stx ptr1+1 ; Save the pointer
207 ; The structure passed to the functions has the same layout as the registers
208 ; of the Commodore REU, so register programming is easy.
216 ; Invalidate the page in the memory window
218 sty curpage+1 ; Y = $FF
220 ; Reload the REU command and start the transfer
225 ; Transfer subroutine for the REU. Expects command in Y.
228 sty REU_COMMAND ; Issue command
230 ldy $01 ; Save the value of the c64 control port...
232 and #$F8 ; Disable ROMs and I/O.
235 lda REU_TRIGGER ; Don't change $FF00
236 sta REU_TRIGGER ; Start the transfer...
238 sty $01 ; Restore the old configuration