started work on SD card support for MEGA65

src/dos_m65/m65_sdcard.s

@@ -0,0 +1,112 @@
+
+;
+; MEGA65 SD/SDHC card support
+;
+
+; Based on https://github.com/MEGA65/mega65-libc/blob/master/cc65/src/sdcard.c
+
+
+
+; Permanent values XXX addresses are temporary
+
+!addr CARD_IS_SDHC = $80 ; $00 = SD, $80 = SDHC
+!addr CARD_SIZE    = $81 ; 4 bytes
+
+; Temporary XXX addresses are temporary
+
+!addr TMP_SECNUM   = $85  ; 4 bytes - sector number
+!addr TMP_STEP     = $89  ; 4 bytes
+
+
+; Hardware
+
+!addr SD_CTL       = $D680
+!addr SD_ADDR      = $D681 ; 4 bytes
+!addr SD_ERRCODE   = $D6DA
+
+
+; XXX SD_SECTORBUF = 0xffd6e00L;
+
+
+
+
+
+
+m65_sdcard_init: ; to be called during DOS initialization
+
+	lda #$00
+	sta CARD_IS_SDHC
+
+	jsr m65_sdcard_reset
+	
+	; FALLTROUGH
+
+m65_sdcard_init_gettype:
+
+	; First work out if this is SD or SDHC card
+	; SD cards can't read at non-sector aligned addresses
+
+	lda #$00
+	sta SD_ADDR+0
+	sta SD_ADDR+1
+	sta SD_ADDR+2
+	sta SD_ADDR+3
+
+	; Trigger read
+
+	lda #$02
+	sta SD_CTL
+
+	; XXX
+
+
+
+	; FALLTROUGH
+
+m65_sdcard_init_getsize:
+
+	; Put $00200000 to TMP_STEP and TMP_SECNUM
+
+	; XXX this should probably be initialized in a loop
+
+	lda #$00
+	sta TMP_SECNUM+0
+	sta TMP_STEP+0
+	sta TMP_SECNUM+1
+	sta TMP_STEP+1
+	sta TMP_SECNUM+3
+	sta TMP_STEP+3
+
+	lda #$02
+	sta TMP_SECNUM+2
+	sta TMP_STEP+2
+
+	;; XXX finish
+
+
+
+
+
+m65_sdcard_reset:
+
+	ldx #$40
+	stx SD_CTL
+	ldy #$00
+	sty SD_CTL
+	iny ; $01
+	sty SD_CTL
+
+	; Wait till SD card resets
+@1:
+	lda SD_CTL
+	and #$03
+	bne @1
+
+	; For SDHC card set appropriate mode
+	
+	bit CARD_IS_SDHC
+	bpl @2
+	inx ; $41
+	stx SD_CTL
+@2:
+	rts