2 ; Extended memory driver for the VDC RAM available on all C128 machines
3 ; version for GEOS enters safe I/O config on C64 (transparent on C128)
5 ; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
8 .include "zeropage.inc"
9 .include "em-kernel.inc"
10 .include "em-error.inc"
14 ; ------------------------------------------------------------------------
15 ; Header. Includes jump table
21 .byte $65, $6d, $64 ; "emd"
22 .byte EMD_API_VERSION ; EM API version number
39 ; ------------------------------------------------------------------------
42 VDC_ADDR_REG = $D600 ; VDC address
43 VDC_DATA_REG = $D601 ; VDC data
45 VDC_DATA_HI = 18 ; used registers
50 ; ------------------------------------------------------------------------
56 .word 64 ; $0000-$3fff as 16k default
58 .word $ffff ; currently mapped-in page (invalid)
63 .res 256 ; memory window
67 ; ------------------------------------------------------------------------
68 ; INSTALL routine. Is called after the driver is loaded into memory. If
69 ; possible, check if the hardware is present and determine the amount of
71 ; Must return an EM_ERR_xx code in a/x.
75 ; do test for VDC presence here???
84 ldx #VDC_CSET ; determine size of RAM...
88 jsr vdcputreg ; turn on 64k
90 jsr settestadr1 ; save original value of test byte
94 lda #$55 ; write $55 here
96 jsr test64k ; read it here and there
97 lda #$aa ; write $aa here
99 jsr test64k ; read it here and there
103 jsr vdcputbyte ; restore original value of test byte
105 lda ptr1 ; do bytes match?
114 jsr vdcputreg ; restore 16/64k flag
115 jmp @endok ; and leave default values for 16k
137 jsr vdcputbyte ; write $55
139 jsr vdcgetbyte ; read here
142 jsr vdcgetbyte ; and there
151 ldy #$02 ; test page 2 (here)
154 ldy #$42 ; or page 64+2 (there)
158 ; ------------------------------------------------------------------------
159 ; UNINSTALL routine. Is called before the driver is removed from memory.
160 ; Can do cleanup or whatever. Must not return anything.
164 ;on C128 restore font and clear the screen?
167 ; ------------------------------------------------------------------------
168 ; PAGECOUNT: Return the total number of available pages in a/x.
176 ; ------------------------------------------------------------------------
177 ; MAP: Map the page in a/x into memory and return a pointer to the page in
178 ; a/x. The contents of the currently mapped page (if any) may be discarded
199 ; copy a single page from (ptr1):VDCRAM to (ptr2):RAM
210 jsr vdcsetsrcaddr ; set source address in VDC
214 @L0: bit VDC_ADDR_REG
216 lda VDC_DATA_REG ; get 2 bytes at a time to speed-up
217 sta (ptr2),y ; (in fact up to 8 bytes could be fetched with special VDC config)
228 ; ------------------------------------------------------------------------
229 ; USE: Tell the driver that the window is now associated with a given page.
232 stx curpage+1 ; Remember the page
234 ldx #>window ; Return the window
237 ; ------------------------------------------------------------------------
238 ; COMMIT: Commit changes in the memory window to extended storage.
241 lda curpage ; jump if no page mapped
253 ; fall through to transferout
255 ; copy a single page from (ptr2):RAM to (ptr1):VDCRAM
266 jsr vdcsetsrcaddr ; set source address in VDC
270 @L0: bit VDC_ADDR_REG
272 lda (ptr2),y ; speedup does not work for writing
281 ; ------------------------------------------------------------------------
282 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
283 ; describing the request is passed in a/x.
284 ; The function must not return anything.
289 beq @L2 ; Skip if no full pages
299 ; Copy the remainder of the page
301 @L2: ldy #EM_COPY::COUNT
302 lda (ptr3),y ; Get bytes in last page
306 ; Transfer the bytes in the last page
325 ; ------------------------------------------------------------------------
326 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
327 ; describing the request is passed in a/x.
328 ; The function must not return anything.
333 beq @L2 ; Skip if no full pages
343 ; Copy the remainder of the page
345 @L2: ldy #EM_COPY::COUNT
346 lda (ptr3),y ; Get bytes in last page
350 ; Transfer the bytes in the last page
369 ;-------------------------------------------------------------------------
370 ; Helper functions to handle VDC ram
376 @L0: bit VDC_ADDR_REG
389 @L0: bit VDC_ADDR_REG
398 @L0: bit VDC_ADDR_REG
403 ; ------------------------------------------------------------------------
404 ; Helper function for COPYFROM and COPYTO: Store the pointer to the request
405 ; structure and prepare data for the copy
410 stx ptr3+1 ; Save the passed em_copy pointer
426 ldy #EM_COPY::COUNT+1
427 lda (ptr3),y ; Get number of pages