2 ; Extended memory driver for the Commodore REU
4 ; Ullrich von Bassewitz, 2002-11-29
7 .include "zeropage.inc"
9 .include "em-kernel.inc"
10 .include "em-error.inc"
17 ; ------------------------------------------------------------------------
18 ; Header. Includes jump table
24 .byte $65, $6d, $64 ; "emd"
25 .byte $00 ; EM API version number
38 ; ------------------------------------------------------------------------
41 REU_STATUS = $DF00 ; Status register
42 REU_COMMAND = $DF01 ; Command register
43 REU_C64ADDR = $DF02 ; C64 base address register
44 REU_REUADDR = $DF04 ; REU base address register
45 REU_COUNT = $DF07 ; Transfer count register
46 REU_IRQMASK = $DF09 ; IRQ mask register
47 REU_CONTROL = $DF0A ; Control register
48 REU_TRIGGER = $FF00 ; REU command trigger
54 ; ------------------------------------------------------------------------
58 pagecount: .res 2 ; Number of pages available
59 curpage: .word $FFFF ; Current page number (invalid)
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.
83 cmp REU_REUADDR ; Check for presence of REU
87 cmp REU_REUADDR ; Check for presence of REU
90 ldx #>(128*4) ; Assume 128KB
92 and #$10 ; Check size bit
94 ldx #>(256*4) ; 256KB when size bit is set
104 lda #<EM_ERR_NO_DEVICE
105 ldx #>EM_ERR_NO_DEVICE
108 ; ------------------------------------------------------------------------
109 ; DEINSTALL routine. Is called before the driver is removed from memory.
110 ; Can do cleanup or whatever. Must not return anything.
117 ; ------------------------------------------------------------------------
118 ; PAGECOUNT: Return the total number of available pages in a/x.
126 ; ------------------------------------------------------------------------
127 ; MAP: Map the page in a/x into memory and return a pointer to the page in
128 ; a/x. The contents of the currently mapped page (if any) may be discarded
133 stx curpage+1 ; Remember the new page
136 jsr common ; Copy the window
139 ldx #>window ; Return the window address
142 ; ------------------------------------------------------------------------
143 ; USE: Tell the driver that the window is now associated with a given page.
146 stx curpage+1 ; Remember the page
148 ldx #>window ; Return the window
151 ; ------------------------------------------------------------------------
152 ; COMMIT: Commit changes in the memory window to extended storage.
155 ldx curpage+1 ; Do we have a page mapped?
156 bmi done ; Jump if no page mapped
173 sty REU_COUNT+1 ; Move 256 bytes
174 bne transfer1 ; Transfer 256 bytes into REU
176 ; ------------------------------------------------------------------------
177 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
178 ; describing the request is passed in a/x.
179 ; The function must not return anything.
186 ; ------------------------------------------------------------------------
187 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
188 ; describing the request is passed in a/x.
189 ; The function must not return anything.
196 ; Remember the passed pointer
199 stx ptr1+1 ; Save the pointer
201 ; The structure passed to the functions has the same layout as the registers
202 ; of the Commodore REU, so register programming is easy.
210 ; Invalidate the page in the memory window
212 sty curpage+1 ; Y = $FF
214 ; Reload the REU command and start the transfer
219 ; Transfer subroutine for the REU. Expects command in Y.
222 sty REU_COMMAND ; Issue command
224 ldy MMU_CR ; Save the current MMU settings
227 sta MMU_CR ; Enable RAM in bank #0
228 lda REU_TRIGGER ; Don't change $FF00
229 sta REU_TRIGGER ; Start the transfer...
231 sty MMU_CR ; Restore the old configuration