2 ; Extended memory driver for the GEORAM cartridge. Driver works without
3 ; problems when statically linked.
5 ; Ullrich von Bassewitz, 2002-11-29
7 ; GEORAM page size checking routine by
8 ; Marco van den Heuvel, 2010-01-21
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
41 ; ------------------------------------------------------------------------
44 GR_WINDOW = $DE00 ; Address of GEORAM window
45 GR_PAGE_LO = $DFFE ; Page register low
46 GR_PAGE_HI = $DFFF ; Page register high
48 ; ------------------------------------------------------------------------
53 pagecount: .res 2 ; Number of available pages
57 ; ------------------------------------------------------------------------
58 ; INSTALL routine. Is called after the driver is loaded into memory. If
59 ; possible, check if the hardware is present and determine the amount of
61 ; Must return an EM_ERR_xx code in a/x.
123 lda #<EM_ERR_NO_DEVICE
124 ldx #>EM_ERR_NO_DEVICE
147 ; rts ; Run into UNINSTALL instead
149 ; ------------------------------------------------------------------------
150 ; UNINSTALL routine. Is called before the driver is removed from memory.
151 ; Can do cleanup or whatever. Must not return anything.
158 ; ------------------------------------------------------------------------
159 ; PAGECOUNT: Return the total number of available pages in a/x.
167 ; ------------------------------------------------------------------------
168 ; USE: Tell the driver that the window is now associated with a given page.
169 ; The GeoRAM cartridge does not copy but actually map the window, so USE is
174 ; ------------------------------------------------------------------------
175 ; MAP: Map the page in a/x into memory and return a pointer to the page in
176 ; a/x. The contents of the currently mapped page (if any) may be discarded
196 ; Use the RTS from COMMIT below to save a precious byte of storage
198 ; ------------------------------------------------------------------------
199 ; COMMIT: Commit changes in the memory window to extended storage.
203 ; ------------------------------------------------------------------------
204 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
205 ; describing the request is passed in a/x.
206 ; The function must not return anything.
214 ; - ptr1 contains the struct pointer
215 ; - ptr2 contains the linear memory buffer
216 ; - ptr3 contains -(count-1)
217 ; - tmp1 contains the low page register value
218 ; - tmp2 contains the high page register value
219 ; - X contains the page offset
232 ; Bump count and repeat
242 @L4: inc tmp1 ; Bump low page register
243 bit tmp1 ; Check for overflow in bit 6
244 bvc @L6 ; Jump if no overflow
252 ; ------------------------------------------------------------------------
253 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
254 ; describing the request is passed in a/x.
255 ; The function must not return anything.
263 ; - ptr1 contains the struct pointer
264 ; - ptr2 contains the linear memory buffer
265 ; - ptr3 contains -(count-1)
266 ; - tmp1 contains the low page register value
267 ; - tmp2 contains the high page register value
268 ; - X contains the page offset
281 ; Bump count and repeat
291 @L4: inc tmp1 ; Bump low page register
292 bit tmp1 ; Check for overflow in bit 6
293 bvc @L6 ; Jump if no overflow
301 ; ------------------------------------------------------------------------
302 ; Helper function for COPYFROM and COPYTO: Store the pointer to the request
303 ; structure and prepare data for the copy
306 stx ptr1+1 ; Save passed pointer
308 ; Get the page number from the struct and adjust it so that it may be used
309 ; with the hardware. That is: lower 6 bits in tmp1, high bits in tmp2.
324 ; Get the buffer pointer into ptr2
333 ; Get the count, calculate -(count-1) and store it into ptr3
344 ; Get the page offset into X and clear Y