started unification of floppy and ramdisk code

src/dos_m65/unit_disk/unit_rd_init.s

@@ -0,0 +1,134 @@
+
+;
+; Initializes DOS part of RAM disk
+;
+
+
+unit_rd_init:
+
+
+	; Copy status string
+
+	ldx #$00
+	stx RD_STATUS_IDX
+	stx RD_CMDFN_IDX
+	stx RD_MODE
+	stx RD_ACPTR_LEN+0
+	stx RD_ACPTR_LEN+1
+	stx RD_ACPTR_PTR+0
+	stx RD_ACPTR_PTR+1
+	dex
+@1:
+	inx
+	lda dos_sts_init_ramdisk,x
+	sta RD_STATUS_BUF,x
+	bne @1
+
+	; FALLTROUGH
+
+unit_rd_init_test_ram:                 ; non-destructive ATTIC/CELLAR RAM test
+
+	; Preserve temporary address area on stack
+
+	ldx #$03
+@2:
+	lda PNTR, x
+	pha
+	dex
+	bpl @2
+
+	stx RD_MSG                         ; $FF - mark no message to be displayed
+
+	; For the start, mark extended RAM as not present
+
+	stx RD_STARTSEG                    ; by default $FF, to mark no RAM disk
+	inx
+	stx RD_VALIDIMG                    ; mark no valid image loaded
+	stx RAM_ATTIC                      ; set ATTIC/CELLAR RAM as not present
+	stx RAM_CELLAR
+
+	; Prepare address - CELLAR RAM, $0880:$0000
+
+	stx PNTR+0
+	stx PNTR+1
+	lda #$80
+	sta PNTR+2
+	lda #$08
+	sta PNTR+3
+
+	ldz #$00
+
+	; Test for CELLAR RAM
+
+	jsr @perform_ram_test
+	bne @done_cellar
+	dec RAM_ATTIC                      ; test passed
+	lda #$08
+	sta RD_STARTSEG                    ; RAM DISK start segment - CELLAR RAM
+
+@done_cellar:
+
+	; Prepare address - ATTIC RAM, $0800:$0000
+
+	lda #$00
+	sta PNTR+2
+
+	; Test for ATTIC RAM
+
+	jsr @perform_ram_test
+	bne @done_attic
+	dec RAM_CELLAR                     ; test passed
+	lda #$00
+	sta RD_STARTSEG                    ; RAM DISK start segment - ATTIC RAM
+
+@done_attic:
+
+	; Restore temporary address area content
+
+	ldx #$00
+@3:
+	pla
+	sta PNTR, x
+	inx
+	cpx #$04
+	bne @3
+
+	; Clear RAM disk device number if no Hyper RAM available
+
+	jsr util_check_rd_ram
+
+	; End of initialization
+
+	rts
+
+@perform_ram_test:
+
+	; Try to change one byte in extended RAM
+
+	lda [PNTR], z
+	tax
+	eor #$FF
+	sta [PNTR], z
+
+	; Make sure the cache does not contain the value any more
+
+	tay
+	dez
+	lda [PNTR], z
+	inz
+	tya
+
+	; Check if byte still contains the new value
+
+	cmp [PNTR], z
+	php
+
+	; Restore byte content
+
+	txa
+	sta [PNTR], z
+	
+	; Return test result
+
+	plp
+	rts