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
25 .byte $65, $6d, $64 ; "emd"
26 .byte EMD_API_VERSION ; EM API version number
39 ; ------------------------------------------------------------------------
42 REU_STATUS = $DF00 ; Status register
43 REU_COMMAND = $DF01 ; Command register
44 REU_C64ADDR = $DF02 ; C64 base address register
45 REU_REUADDR = $DF04 ; REU base address register
46 REU_COUNT = $DF07 ; Transfer count register
47 REU_IRQMASK = $DF09 ; IRQ mask register
48 REU_CONTROL = $DF0A ; Control register
49 REU_TRIGGER = $FF00 ; REU command trigger
55 ; ------------------------------------------------------------------------
59 pagecount: .res 2 ; Number of pages available
60 curpage: .res 2 ; Current page number
62 window: .res 256 ; Memory "window"
64 reu_params: .word $0000 ; Host address, lo, hi
65 .word $0000 ; Exp address, lo, hi
66 .byte $00 ; Expansion bank no.
67 .word $0000 ; # bytes to move, lo, hi
68 .byte $00 ; Interrupt mask reg.
69 .byte $00 ; Adress control reg.
73 ; ------------------------------------------------------------------------
74 ; INSTALL routine. Is called after the driver is loaded into memory. If
75 ; possible, check if the hardware is present and determine the amount of
77 ; Must return an EM_ERR_xx code in a/x.
81 ldx #$00 ; High byte of return code
84 cmp REU_REUADDR ; Check for presence of REU
88 cmp REU_REUADDR ; Check for presence of REU
91 ldy #>(128*4) ; Assume 128KB
93 and #$10 ; Check size bit
95 ldy #>(256*4) ; 256KB when size bit is set
100 sty curpage+1 ; Invalidate the current page
101 txa ; X = A = EM_ERR_OK
107 lda #EM_ERR_NO_DEVICE
108 ; rts ; Run into UNINSTALL instead
110 ; ------------------------------------------------------------------------
111 ; UNINSTALL routine. Is called before the driver is removed from memory.
112 ; Can do cleanup or whatever. Must not return anything.
119 ; ------------------------------------------------------------------------
120 ; PAGECOUNT: Return the total number of available pages in a/x.
128 ; ------------------------------------------------------------------------
129 ; MAP: Map the page in a/x into memory and return a pointer to the page in
130 ; a/x. The contents of the currently mapped page (if any) may be discarded
135 stx curpage+1 ; Remember the new page
138 jsr common ; Copy the window
141 ldx #>window ; Return the window address
144 ; ------------------------------------------------------------------------
145 ; USE: Tell the driver that the window is now associated with a given page.
148 stx curpage+1 ; Remember the page
150 ldx #>window ; Return the window
153 ; ------------------------------------------------------------------------
154 ; COMMIT: Commit changes in the memory window to extended storage.
157 ldx curpage+1 ; Do we have a page mapped?
158 bmi done ; Jump if no page mapped
175 sty REU_COUNT+1 ; Move 256 bytes
176 bne transfer1 ; Transfer 256 bytes into REU
178 ; ------------------------------------------------------------------------
179 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
180 ; describing the request is passed in a/x.
181 ; The function must not return anything.
188 ; ------------------------------------------------------------------------
189 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
190 ; describing the request is passed in a/x.
191 ; The function must not return anything.
198 ; Remember the passed pointer
201 stx ptr1+1 ; Save the pointer
203 ; The structure passed to the functions has the same layout as the registers
204 ; of the Commodore REU, so register programming is easy.
212 ; Invalidate the page in the memory window
214 sty curpage+1 ; Y = $FF
216 ; Reload the REU command and start the transfer
221 ; Transfer subroutine for the REU. Expects command in Y.
224 sty REU_COMMAND ; Issue command
226 ldy MMU_CR ; Save the current MMU settings
229 sta MMU_CR ; Enable RAM in bank #0
230 lda REU_TRIGGER ; Don't change $FF00
231 sta REU_TRIGGER ; Start the transfer...
233 sty MMU_CR ; Restore the old configuration