2 ; Extended memory driver for the C64 D2TV (the second or PAL version).
3 ; Driver works without problems when statically linked.
5 ; Ullrich von Bassewitz, 2005-11-27
9 .include "zeropage.inc"
11 .include "em-kernel.inc"
12 .include "em-error.inc"
20 ; ------------------------------------------------------------------------
21 ; Header. Includes jump table
23 module_header _dtv_himem_emd
27 .byte $65, $6d, $64 ; "emd"
28 .byte EMD_API_VERSION ; EM API version number
45 ; ------------------------------------------------------------------------
48 OP_COPYFROM = %00001101
51 START_BANK = 2 ; Start at $20000
52 PAGES = (2048 - 128) * 4
55 ; ------------------------------------------------------------------------
59 window: .res 256 ; Memory "window"
63 ; The MAP and COMMIT entries will actually call COPYFROM/COPYTO with
64 ; a pointer to the following data structure:
66 dma_params: .word window ; Host address
67 .byte 0 ; Offset in page
68 curpage: .word $0000 ; Page
69 .word .sizeof (window); # bytes to move, lo, hi
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.
96 lda #<EM_ERR_NO_DEVICE
97 ldx #>EM_ERR_NO_DEVICE
102 stx curpage+1 ; Invalidate curpage
104 txa ; A/X = EM_ERR_OK
106 ; rts ; Run into UNINSTALL instead
108 ; ------------------------------------------------------------------------
109 ; UNINSTALL routine. Is called before the driver is removed from memory.
110 ; Can do cleanup or whatever. Must not return anything.
116 ; ------------------------------------------------------------------------
117 ; PAGECOUNT: Return the total number of available pages in a/x.
125 ; ------------------------------------------------------------------------
126 ; MAP: Map the page in a/x into memory and return a pointer to the page in
127 ; a/x. The contents of the currently mapped page (if any) may be discarded
132 stx curpage+1 ; Remember the new page
136 jsr COPYFROM ; Copy data into 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.
154 COMMIT: lda curpage+1 ; Do we have a page mapped?
155 bmi done ; Jump if no page mapped
162 ; ------------------------------------------------------------------------
163 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
164 ; describing the request is passed in a/x.
165 ; The function must not return anything.
169 stx ptr1+1 ; Save the pointer
171 ldx #OP_COPYTO ; Load the command
174 ; ------------------------------------------------------------------------
175 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
176 ; describing the request is passed in a/x.
177 ; The function must not return anything.
182 stx ptr1+1 ; Save the pointer
186 ; DTV DMA transfer routine. Expects the command in X.
187 ; NOTE: We're using knowledge about field order in the EM_COPY struct here!
190 jsr WAIT ; Wait until DMA is finished
197 ; Setup the target address and the source and target steps. Y contains zero,
198 ; which is EM_COPY::BUF.
200 sty $d307 ; Source step high = 0
201 sty $d309 ; Dest step high = 0
203 sta $d303 ; Dest address low
205 sty $d306 ; Source step low = 1
206 sty $d308 ; Dest step low = 1
209 lda #$40 ; Dest is always RAM, start at $00000
212 ; Setup the source address. Incrementing Y will make it point to EM_COPY::OFFS.
213 ; We will allow page numbers higher than PAGES and map them to ROM. This will
214 ; allow reading the ROM by specifying a page starting with PAGES.
224 adc #START_BANK ; Carry clear here from WAIT
226 cmp #>PAGES+START_BANK ; Valid range?
228 ora #$40 ; Address RAM
244 ; Wait until DMA is done