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
45 ; ------------------------------------------------------------------------
48 GR_WINDOW = $DE00 ; Address of GEORAM window
49 GR_PAGE_LO = $DFFE ; Page register low
50 GR_PAGE_HI = $DFFF ; Page register high
52 ; ------------------------------------------------------------------------
57 pagecount: .res 2 ; Number of available pages
61 ; ------------------------------------------------------------------------
62 ; INSTALL routine. Is called after the driver is loaded into memory. If
63 ; possible, check if the hardware is present and determine the amount of
65 ; Must return an EM_ERR_xx code in a/x.
123 lda #<EM_ERR_NO_DEVICE
124 ldx #>EM_ERR_NO_DEVICE
145 ; rts ; Run into UNINSTALL instead
147 ; ------------------------------------------------------------------------
148 ; UNINSTALL routine. Is called before the driver is removed from memory.
149 ; Can do cleanup or whatever. Must not return anything.
156 ; ------------------------------------------------------------------------
157 ; PAGECOUNT: Return the total number of available pages in a/x.
165 ; ------------------------------------------------------------------------
166 ; USE: Tell the driver that the window is now associated with a given page.
167 ; The GeoRAM cartridge does not copy but actually map the window, so USE is
172 ; ------------------------------------------------------------------------
173 ; MAP: Map the page in a/x into memory and return a pointer to the page in
174 ; a/x. The contents of the currently mapped page (if any) may be discarded
194 ; Use the RTS from COMMIT below to save a precious byte of storage
196 ; ------------------------------------------------------------------------
197 ; COMMIT: Commit changes in the memory window to extended storage.
201 ; ------------------------------------------------------------------------
202 ; COPYFROM: Copy from extended into linear memory. A pointer to a structure
203 ; describing the request is passed in a/x.
204 ; The function must not return anything.
212 ; - ptr1 contains the struct pointer
213 ; - ptr2 contains the linear memory buffer
214 ; - ptr3 contains -(count-1)
215 ; - tmp1 contains the low page register value
216 ; - tmp2 contains the high page register value
217 ; - X contains the page offset
230 ; Bump count and repeat
240 @L4: inc tmp1 ; Bump low page register
241 bit tmp1 ; Check for overflow in bit 6
242 bvc @L6 ; Jump if no overflow
250 ; ------------------------------------------------------------------------
251 ; COPYTO: Copy from linear into extended memory. A pointer to a structure
252 ; describing the request is passed in a/x.
253 ; The function must not return anything.
261 ; - ptr1 contains the struct pointer
262 ; - ptr2 contains the linear memory buffer
263 ; - ptr3 contains -(count-1)
264 ; - tmp1 contains the low page register value
265 ; - tmp2 contains the high page register value
266 ; - X contains the page offset
279 ; Bump count and repeat
289 @L4: inc tmp1 ; Bump low page register
290 bit tmp1 ; Check for overflow in bit 6
291 bvc @L6 ; Jump if no overflow
299 ; ------------------------------------------------------------------------
300 ; Helper function for COPYFROM and COPYTO: Store the pointer to the request
301 ; structure and prepare data for the copy
304 stx ptr1+1 ; Save passed pointer
306 ; Get the page number from the struct and adjust it so that it may be used
307 ; with the hardware. That is: lower 6 bits in tmp1, high bits in tmp2.
322 ; Get the buffer pointer into ptr2
331 ; Get the count, calculate -(count-1) and store it into ptr3
342 ; Get the page offset into X and clear Y