2 ; Extended memory driver for the VDC RAM available on all C128 machines
3 ; (based on code by Ullrich von Bassewitz)
4 ; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
8 ; Marco van den Heuvel, 2010-01-22
11 .include "zeropage.inc"
13 .include "em-kernel.inc"
14 .include "em-error.inc"
20 ; ------------------------------------------------------------------------
21 ; Header. Includes jump table
27 .byte $65, $6d, $64 ; "emd"
28 .byte EMD_API_VERSION ; EM API version number
45 ; ------------------------------------------------------------------------
48 VDC_ADDR_REG = $D600 ; VDC address
49 VDC_DATA_REG = $D601 ; VDC data
51 VDC_DATA_HI = 18 ; used registers
56 ; ------------------------------------------------------------------------
61 pagecount: .word 64 ; $0000-$3fff as 16k default
62 curpage: .word $ffff ; currently mapped-in page (invalid)
66 window: .res 256 ; memory window
70 ; ------------------------------------------------------------------------
71 ; INSTALL routine. Is called after the driver is loaded into memory. If
72 ; possible, check if the hardware is present and determine the amount of
74 ; Must return an EM_ERR_xx code in a/x.
80 lda #VDC_CSET ; determine size of RAM...
89 lda #<EM_ERR_NO_DEVICE
90 ldx #>EM_ERR_NO_DEVICE
94 ldx #VDC_CSET ; determine size of RAM...
98 jsr vdcputreg ; turn on 64k
100 jsr settestadr1 ; save original value of test byte
104 lda #$55 ; write $55 here
106 jsr test64k ; read it here and there
107 lda #$aa ; write $aa here
109 jsr test64k ; read it here and there
113 jsr vdcputbyte ; restore original value of test byte
115 lda ptr1 ; do bytes match?
124 jsr vdcputreg ; restore 16/64k flag
125 jmp @endok ; and leave default values for 16k
144 jsr vdcputbyte ; write $55
146 jsr vdcgetbyte ; read here
149 jsr vdcgetbyte ; and there
158 ldy #$02 ; test page 2 (here)
161 ldy #$42 ; or page 64+2 (there)
165 ; ------------------------------------------------------------------------
166 ; UNINSTALL routine. Is called before the driver is removed from memory.
167 ; Can do cleanup or whatever. Must not return anything.
171 ;on C128 restore font and clear the screen?
174 ; ------------------------------------------------------------------------
175 ; PAGECOUNT: Return the total number of available pages in a/x.
183 ; ------------------------------------------------------------------------
184 ; MAP: Map the page in a/x into memory and return a pointer to the page in
185 ; a/x. The contents of the currently mapped page (if any) may be discarded
206 ; copy a single page from (ptr1):VDCRAM to (ptr2):RAM
211 jsr vdcsetsrcaddr ; set source address in VDC
215 @L0: bit VDC_ADDR_REG
217 lda VDC_DATA_REG ; get 2 bytes at a time to speed-up
218 sta (ptr2),y ; (in fact up to 8 bytes could be fetched with special VDC config)
226 ; ------------------------------------------------------------------------
227 ; USE: Tell the driver that the window is now associated with a given page.
230 stx curpage+1 ; Remember the page
232 ldx #>window ; Return the window
235 ; ------------------------------------------------------------------------
236 ; COMMIT: Commit changes in the memory window to extended storage.
239 lda curpage ; jump if no page mapped
251 ; fall through to transferout
253 ; copy a single page from (ptr2):RAM to (ptr1):VDCRAM
258 jsr vdcsetsrcaddr ; set source address in VDC
262 @L0: bit VDC_ADDR_REG
264 lda (ptr2),y ; speedup does not work for writing
270 ; ------------------------------------------------------------------------
271 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
272 ; describing the request is passed in a/x.
273 ; The function must not return anything.
278 beq @L2 ; Skip if no full pages
288 ; Copy the remainder of the page
290 @L2: ldy #EM_COPY::COUNT
291 lda (ptr3),y ; Get bytes in last page
295 ; Transfer the bytes in the last page
306 ; ------------------------------------------------------------------------
307 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
308 ; describing the request is passed in a/x.
309 ; The function must not return anything.
314 beq @L2 ; Skip if no full pages
324 ; Copy the remainder of the page
326 @L2: ldy #EM_COPY::COUNT
327 lda (ptr3),y ; Get bytes in last page
331 ; Transfer the bytes in the last page
342 ;-------------------------------------------------------------------------
343 ; Helper functions to handle VDC ram
349 @L0: bit VDC_ADDR_REG
362 @L0: bit VDC_ADDR_REG
371 @L0: bit VDC_ADDR_REG
376 ; ------------------------------------------------------------------------
377 ; Helper function for COPYFROM and COPYTO: Store the pointer to the request
378 ; structure and prepare data for the copy
383 stx ptr3+1 ; Save the passed em_copy pointer
399 ldy #EM_COPY::COUNT+1
400 lda (ptr3),y ; Get number of pages