[DOS/FAT32] enable selection of auto_tx and the fast write loop via U…

…0>B (X16Community#306)

* [DOS/FAT32] enable selection of auto_tx and the fast write loop via U0>B

* we are not using the rest of the byte, but we should also avoid setting extraneous bits in it

* handle initialization

dos/functions.s

@@ -1095,10 +1095,10 @@ test_rom_checksum:
 ;---------------------------------------------------------------
 ; set_fast_serial
 ;
-; In:   a  fast serial (0/1)
+; In:   a  fast serial (0/1/2/3)
 ;---------------------------------------------------------------
 set_fast_serial:
-	; do nothing
+	fat32_call sdcard_set_fast_mode
 	lda #0
 	rts
 

fat32/fat32.s

@@ -9,7 +9,7 @@
 .include "sdcard.inc"
 .include "text_input.inc"
 
-.import sector_buffer, sector_buffer_end, sector_lba
+.import sector_buffer, sector_buffer_end, sector_lba, sdcard_set_fast_mode
 
 .import filename_char_ucs2_to_internal, filename_char_internal_to_ucs2
 .import filename_cp437_to_internal, filename_char_internal_to_cp437
@@ -1246,6 +1246,9 @@ fat32_init:
 	; No time set up
 	sta fat32_time_year
 
+	lda #0 ; default to slow/traditional SD accesses
+	jsr sdcard_set_fast_mode
+
 	sec
 	rts
 

fat32/main.s

@@ -54,6 +54,7 @@
 
 .import sdcard_init
 .import sdcard_check_alive
+.import sdcard_set_fast_mode
 
 .import fat32_set_time
 
@@ -103,3 +104,5 @@
 
 	jmp sdcard_init             ; $C069
 	jmp sdcard_check_alive      ; $C06C
+
+	jmp sdcard_set_fast_mode    ; $C06F

fat32/regs.inc

@@ -54,5 +54,5 @@ ERRNO_OUT_OF_RESOURCES = 12
 SPI_CTRL_SELECT_SDCARD = $01
 SPI_CTRL_SELECT_MASK   = $01
 SPI_CTRL_SLOWCLK       = $02
-SPI_CTRL_AUTOTX        = $08
+SPI_CTRL_AUTOTX        = $04
 SPI_CTRL_BUSY          = $80

fat32/sdcard.s

@@ -6,7 +6,7 @@
 	.include "lib.inc"
 	.include "sdcard.inc"
 
-	.export sector_buffer, sector_buffer_end, sector_lba
+	.export sector_buffer, sector_buffer_end, sector_lba, sdcard_set_fast_mode
 
 	.bss
 cmd_idx = sdcard_param
@@ -22,14 +22,11 @@ sdcard_param:
 sector_lba:
 	.res 4 ; dword (part of sdcard_param) - LBA of sector to read/write
 	.res 1
+sd_fast:
+	.res 1 ; Bitmask: WR------ where R = auto_tx and W = fast writes
 
 timeout_cnt:       .byte 0
 
-; XXX disabled for now; on real hardware, this returns
-; XXX all 0xFE bytes with all tested SD cards
-;FAST_READ=1
-;FAST_WRITE=1
-
 	.code
 
 ;-----------------------------------------------------------------------------
@@ -329,8 +326,39 @@ sdcard_read_sector:
 	clc
 	rts
 
-.ifdef FAST_READ
-@start:	; Enable auto-tx mode
+@start:
+	bit sd_fast
+	bvs @fast
+
+@slow:
+	; Read 512 bytes of sector data
+	ldx #$FF
+	ldy #0
+@3:	stx SPI_DATA		; 4
+@4:	bit SPI_CTRL		; 4
+	bmi @4			; 2 + 1 if branch
+
+	lda SPI_DATA		; 4
+	sta sector_buffer + 0, y
+	iny
+	bne @3
+
+	; Y already 0 at this point
+@5:	stx SPI_DATA		; 4
+@6:	bit SPI_CTRL		; 4
+	bmi @6			; 2 + 1 if branch
+	lda SPI_DATA		; 4
+	sta sector_buffer + 256, y
+	iny
+	bne @5
+
+	; Read CRC bytes
+	jsr spi_read
+	jsr spi_read
+
+	jmp @after
+@fast:
+	; Enable auto-tx mode
 	lda SPI_CTRL
 	ora #SPI_CTRL_AUTOTX
 	sta SPI_CTRL
@@ -341,7 +369,7 @@ sdcard_read_sector:
 
 	; Efficiently read first 256 bytes (hide SPI transfer time)
  	ldy #0				; 2
-@3:	lda SPI_DATA			; 4
+@3f:	lda SPI_DATA			; 4
 	sta sector_buffer + 0, y	; 5
 	lda SPI_DATA			; 4
 	sta sector_buffer + 1, y	; 5
@@ -361,10 +389,10 @@ sdcard_read_sector:
 	clc				; 2
 	adc #8				; 2
 	tay				; 2
-	bne @3				; 2+1
+	bne @3f				; 2+1
 
 	; Efficiently read second 256 bytes (hide SPI transfer time)
-@4:	lda SPI_DATA			; 4
+@4f:	lda SPI_DATA			; 4
 	sta sector_buffer + 256 + 0, y	; 5
 	lda SPI_DATA			; 4
 	sta sector_buffer + 256 + 1, y	; 5
@@ -384,7 +412,7 @@ sdcard_read_sector:
 	clc				; 2
 	adc #8				; 2
 	tay				; 2
-	bne @4				; 2+1
+	bne @4f				; 2+1
 
 	; Disable auto-tx mode
 	lda SPI_CTRL
@@ -393,33 +421,7 @@ sdcard_read_sector:
 
 	; Next read is now already done (first CRC byte), read second CRC byte
 	jsr spi_read
-
-.else
-@start:	; Read 512 bytes of sector data
-	ldx #$FF
-	ldy #0
-@3:	stx SPI_DATA		; 4
-@4:	bit SPI_CTRL		; 4
-	bmi @4			; 2 + 1 if branch
-
-	lda SPI_DATA		; 4
-	sta sector_buffer + 0, y
-	iny
-	bne @3
-
-	; Y already 0 at this point
-@5:	stx SPI_DATA		; 4
-@6:	bit SPI_CTRL		; 4
-	bmi @6			; 2 + 1 if branch
-	lda SPI_DATA		; 4
-	sta sector_buffer + 256, y
-	iny
-	bne @5
-
-	; Read CRC bytes
-	jsr spi_read
-	jsr spi_read
-.endif
+@after:
 	; Success
 	jsr deselect
 	sec
@@ -448,22 +450,24 @@ sdcard_write_sector:
 	lda #$FE
 	jsr spi_write
 
-.ifdef FAST_WRITE
+	bit sd_fast
+	bpl @slow
 	; Send 512 bytes of sector data
 	; NOTE: Direct access of SPI registers to speed up.
 	;       Make sure 9 CPU clock cycles take longer than 640 ns (eg. CPU max 14MHz)
 	ldy #0
-@1:	lda sector_buffer, y		; 4
+@1f:	lda sector_buffer, y		; 4
 	sta SPI_DATA			; 4
 	iny				; 2
-	bne @1				; 2 + 1
+	bne @1f				; 2 + 1
 
 	; Y already 0 at this point
-@2:	lda sector_buffer + 256, y	; 4
+@2f:	lda sector_buffer + 256, y	; 4
 	sta SPI_DATA			; 4
 	iny				; 2
-	bne @2				; 2 + 1
-.else
+	bne @2f				; 2 + 1
+	bra @after
+@slow:
 	; Send 512 bytes of sector data
 	ldy #0
 @1:	lda sector_buffer, y		; 4
@@ -476,7 +480,7 @@ sdcard_write_sector:
 	spi_write_macro
 	iny				; 2
 	bne @2				; 2 + 1
-.endif
+@after:
 	; Dummy CRC
 	lda #0
 	jsr spi_write
@@ -558,3 +562,24 @@ sdcard_check_alive:
 	jsr deselect
 	plp
 	rts
+
+;-----------------------------------------------------------------------------
+; sdcard_set_fast_mode
+;
+; .A = 0: fast mode off
+; .A = 1: fast reads
+; .A = 2: fast writes
+; .A = 3: fast reads and writes
+;-----------------------------------------------------------------------------
+sdcard_set_fast_mode:
+	pha
+	lda #$c0
+	trb sd_fast
+	pla
+	and #3
+	lsr
+	ror
+	ror
+	tsb sd_fast
+	sec
+	rts

inc/fat32.inc

@@ -43,3 +43,4 @@ fat32_set_time          = $C066
 sdcard_init             = $C069
 sdcard_check_alive      = $C06C
 
+sdcard_set_fast_mode    = $C06F