more work towards SD card support

src/dos_m65/sdcard/sdcard_helpers.s

@@ -75,6 +75,8 @@ sdcard_helper_fail:
 
 sdcard_wait_ready:
 
+	; XXX if card does not get ready, try to reset it
+
 	lda SD_CTL
 	; Sometimes we see this result, i.e., sdcard.vhdl thinks it is done,
 	; but sdcardio.vhdl thinks not. This means a read error.

src/dos_m65/sdcard/sdcard_writesector.s

@@ -42,23 +42,50 @@ sdcard_writesector_try_loop:
 
 	jsr sdcard_writesector_copy_data
 
+	; Wait till card is ready
 
+	jsr sdcard_wait_ready
+	bcs sdcard_writesector_fail
 
+	; Write command
 
+	lda #CARD_CMD_WRITE                ; $03
+	sta SD_CTL
 
+	; Wait for command completion
 
+	jsr sdcard_wait_ready
+	bcs sdcard_writesector_fail
 
+	; Check result
 
+	lda SD_CTL
+	and #$67
+	bne sdcard_writesector_verify
 
+	; Write failed - retry
 
+	jsr sdcard_reset
+	dec CARD_TMP_RETRIES
+	bne sdcard_writesector_try_loop
 
-
+	; FALLTROUGH
 
 sdcard_writesector_fail:
 
 	sec
 	rts
 
+sdcard_writesector_verify:
+
+	; There is a bug in the SD controller; you have to read between writes,
+	; or it gets really upset
+
+	; XXX
+
+
+
+