From 32a73bb5f8d1dda5eb37aa25804af3a334600363 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Mon, 28 Sep 2020 19:10:54 +0200
Subject: [PATCH] more work on SD card support

---
 src/dos_m65/sdcard/sdcard_helpers.s     | 66 +++++++++++++++++++++
 src/dos_m65/sdcard/sdcard_readsector.s  | 38 +-----------
 src/dos_m65/sdcard/sdcard_writesector.s | 78 +++++++++++++++++++++++++
 3 files changed, 147 insertions(+), 35 deletions(-)
 create mode 100644 src/dos_m65/sdcard/sdcard_helpers.s
 create mode 100644 src/dos_m65/sdcard/sdcard_writesector.s

diff --git a/src/dos_m65/sdcard/sdcard_helpers.s b/src/dos_m65/sdcard/sdcard_helpers.s
new file mode 100644
index 00000000..d53a2c8e
--- /dev/null
+++ b/src/dos_m65/sdcard/sdcard_helpers.s
@@ -0,0 +1,66 @@
+
+;
+; Various helper routines for SD card support
+;
+
+; Based on https://github.com/MEGA65/mega65-libc/blob/master/cc65/src/sdcard.c
+
+
+
+;
+; Sets read/write address
+;
+; Input: CARD_SECNUM, CARD_IS_SDHC
+; Output: Carry set = error
+; Preserves: .X, .Y, .Z
+;
+
+sdcard_set_addr:
+
+	bit CARD_IS_SDHC
+	bpl sdcard_set_addr_sdsc
+
+sdcard_set_addr_sdhc:
+
+	lda CARD_SECNUM+0
+	sta SD_ADDR+0
+	lda CARD_SECNUM+1
+	sta SD_ADDR+1
+	lda CARD_SECNUM+2
+	sta SD_ADDR+2
+	lda CARD_SECNUM+3
+	sta SD_ADDR+3
+
+	; FALLTROUGH
+
+sdcard_set_addr_done:
+
+	clc
+	rts
+
+sdcard_set_addr_sdsc:
+
+	; Multiply sector number by 512
+
+	lda #$00
+	sta SD_ADDR+0
+	clc
+	lda CARD_SECNUM+0
+	rol
+	sta SD_ADDR+1
+	lda CARD_SECNUM+1
+	rol
+	sta SD_ADDR+2
+	lda CARD_SECNUM+2
+	rol
+	sta SD_ADDR+3
+	bcs sdcard_set_addr_fail                 ; branch if sector number too large for SD card
+	lda CARD_SECNUM+3
+	beq sdcard_set_addr_done                 ; do not branch if sector number too large for SD card
+
+	; FALLTROUGH
+
+sdcard_set_addr_fail:
+
+	sec
+	rts
diff --git a/src/dos_m65/sdcard/sdcard_readsector.s b/src/dos_m65/sdcard/sdcard_readsector.s
index 1f20ae9b..8fe2194d 100644
--- a/src/dos_m65/sdcard/sdcard_readsector.s
+++ b/src/dos_m65/sdcard/sdcard_readsector.s
@@ -13,41 +13,10 @@ sdcard_readsector:
 
 	; XXX check if card initialized and operable
 
-	; Set read address, depending on card type
+	; Set read address
 
-	bit CARD_IS_SDHC
-	bpl sdcard_readsector_sdsc
-
-sdcard_readsector_sdhc:
-
-	lda CARD_SECNUM+0
-	sta SD_ADDR+0
-	lda CARD_SECNUM+1
-	sta SD_ADDR+1
-	lda CARD_SECNUM+2
-	sta SD_ADDR+2
-	lda CARD_SECNUM+3
-	sta SD_ADDR+3
-
-	bra sdcard_readsector_read
-
-sdcard_readsector_sdsc: ; multiply sector number by 512
-
-	lda #$00
-	sta SD_ADDR+0
-	clc
-	lda CARD_SECNUM+0
-	rol
-	sta SD_ADDR+1
-	lda CARD_SECNUM+1
-	rol
-	sta SD_ADDR+2
-	lda CARD_SECNUM+2
-	rol
-	sta SD_ADDR+3
-	bcs sdcard_readsector_fail               ; branch if sector number too large for SD card
-	lda CARD_SECNUM+3
-	bne sdcard_readsector_fail               ; branch if sector number too large for SD card
+	jsr sdcard_set_addr
+	bcs sdcard_readsector_fail 
 
 	; FALLTROUGH
 
@@ -100,7 +69,6 @@ sdcard_readsector_fail:
 
 sdcard_readsector_copy_data:
 
-	; XXX this should be a separate routine
 	; XXX use DMAgic for this
 
 	phz
diff --git a/src/dos_m65/sdcard/sdcard_writesector.s b/src/dos_m65/sdcard/sdcard_writesector.s
new file mode 100644
index 00000000..851f6d44
--- /dev/null
+++ b/src/dos_m65/sdcard/sdcard_writesector.s
@@ -0,0 +1,78 @@
+
+;
+; Writes the sector to the SD card
+;
+
+; Based on https://github.com/MEGA65/mega65-libc/blob/master/cc65/src/sdcard.c
+
+
+; XXX finish, provide documentation
+
+
+sdcard_writesector:
+
+	; XXX check if card initialized and operable
+
+	lda SD_CTL
+	and #$03
+	bne sdcard_writesector             ; XXX add a timer here
+
+	; End reset
+
+	lda #$01
+	sta SD_CTL
+
+	; Set write address
+
+	jsr sdcard_set_addr
+
+
+
+
+
+
+
+	jsr sdcard_writesector_copy_data
+
+
+
+
+
+
+
+
+
+
+;
+; Helper routines
+;
+
+sdcard_writesector_copy_data:
+
+	; XXX use DMAgic for this
+
+	phz
+	phx
+
+	ldx #$00
+	ldz #$00
+
+@1:
+	lda CARD_BUF,x
+	sta [CARD_BUFPNT],z
+	inc CARD_BUFPNT+1
+	lda CARD_BUF+$100,x
+	sta [CARD_BUFPNT],z
+	dec CARD_BUFPNT+1	
+
+	inz
+	inx
+	bne @1
+
+	; Restore registers and quit
+
+	plx
+	plz
+
+	clc
+	rts