> Any suggestions would be great

Ted, here's the initialisation sequence I'm using with a dsPIC and
4GB and 8GB SDHC cards, both standard and micro

My experience with various makes of cards so far has made me
wary of some substitution problems, so it's a work in progress,
but initialisation seems reliable

Joe

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
;          Initialise SD card
;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

cmd00  =3D  0 + 0x40    ;reset
cmd01  =3D  1 + 0x40
cmd02  =3D  2 + 0x40
cmd05  =3D  5 + 0x40
cmd08  =3D  8 + 0x40
cmd09  =3D  9 + 0x40    ;fetch CSD
cmd10  =3D 10 + 0x40    ;fetch CID
cmd12  =3D 12 + 0x40
cmd13  =3D 13 + 0x40    ;fetch Status Register
cmd16  =3D 16 + 0x40    ;set block length
cmd17  =3D 17 + 0x40    ;read single block of 512 bytes
cmd18  =3D 18 + 0x40    ;read multiple blocks
acmd22 =3D 22 + 0x40
acmd23 =3D 23 + 0x40
cmd24  =3D 24 + 0x40    ;write 1 block of 512 bytes
cmd25  =3D 25 + 0x40    ;write multiple blocks
acmd41 =3D 41 + 0x40    ;CRC 0x69
acmd51 =3D 51 + 0x40    ;fetch SCR
cmd55  =3D 55 + 0x40    ;CRC 0x77
cmd58  =3D 58 + 0x40    ;fetch OCR

           mov     #0b0000000100101101,w0  ;start SPI at 368.64kHz
;                     xxx
;                        0                  Clk controlled by module
;                         0                 SDO controlled by module
;                          0                8-bit transfers
;                           0               input sampled in middle of bit
;                            1              CPHA =3D 0, rising-edge
;                             0             /SS as normal I/O pin
;                              0            CPOL =3D 0, idle low
;                               1           Master
;                                011                             6:1
;                                   01                          16:1 ->=20
353kHz (33.88MHz/96)
;                                101                             3:1
;                                   11                           1:1 ->=20
9.8304MHz (29.4912/3)
;                                100                             4:1 ->=20
7.3728MHz (29.4912/4)
;                                   11                           1:1
           mov     w0,SPI1CON1

;http://ww1.microchip.com/downloads/en/AppNotes/01069B.pdf
;Using C30 Compiler and the SPI module to Interface EEPROMs with dsPIC33F=20
and PIC24F

card_init: bclr    SPI1CON1,#MODE16
           bset    SPI1CON1,#SMP

           bset    SPI1STAT,#SPIEN         ;enable SPI module

           bset    LATB,#cs                ;card /CS inactive
           call    usec100

;send > 74 dummy clocks with DI high

           mov     #10,w1
           mov     #0xff,w0
do74:      call    send_w0
           dec     w1,w1
           bra     nz,do74

           call    usec100
           bclr    LATB,#cs                ;card /CS active
           call    usec100

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

;send CMD0 + argument<31:0> 00 00 00 00 + CRC
;
;http://ghsi.de/CRC/index.php?Polynom=3D10001000&Message=3D40+00+00+00+00
;
;10001000, =3D x^7 + x^3
;String =3D 40 00 00 00 00
;Result =3D 1001010 =3D $4a, +1 =3D 10010101 =3D $95

           mov     #cmd00,w0
           call    send_w0
           mov     #0x00,w0
           call    send_w0
           call    send_w0
           call    send_w0
           call    send_w0
           mov     #0x95,w0
           call    send_w0

;wait for '0x01' response

more_00r:  mov     #0xff,w0                ;supply CLK, wait for response
           call    send_w0                 ;with SDO high (FF data)
           bclr    SPI1STAT,#SPIROV        ;must clear overflow flag
           btss    SPI1STAT,#SPIRBF        ;test for full receive buffer
           bra     $-2
           mov     SPI1BUF,w2              ;read buffer
           mov     #0x01,w1                ;wait for CMD0 '0x01' response
           xor     w1,w2,w1
           bra     nz,more_00r

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

;send CMD8 + argument<31:0> 00 00 01 AA + 7-bit CRC + 1 (end bit)
;String =3D 48 00 00 01 AA
;Result =3D 1000011 =3D $43, +1 =3D 10000111 =3D> $87

           mov     #cmd08,w0
           call    send_w0
           mov     #0x00,w0
           call    send_w0
           call    send_w0
           mov     #0x01,w0
           call    send_w0
           mov     #0xaa,w0                ;check pattern
           call    send_w0
           mov     #0x87,w0
           call    send_w0

;wait for '0x01' response

more_08r:  mov     #0xff,w0
           call    send_w0
           bclr    SPI1STAT,#SPIROV
           btss    SPI1STAT,#SPIRBF
           bra     $-2
           mov     SPI1BUF,w2
           mov     #0x01,w1                ;wait for CMD8 '0x01' response
           xor     w1,w2,w1
           bra     nz,more_08r

;pick up next 32 bits

           mov     #0xff,w0
           call    send_w0
           bclr    SPI1STAT,#SPIROV
           btss    SPI1STAT,#SPIRBF
           bra     $-2
           mov     SPI1BUF,w2

           mov     #0xff,w0
           call    send_w0
           bclr    SPI1STAT,#SPIROV
           btss    SPI1STAT,#SPIRBF
           bra     $-2
           mov     SPI1BUF,w2

           mov     #0xff,w0
           call    send_w0
           bclr    SPI1STAT,#SPIROV
           btss    SPI1STAT,#SPIRBF
           bra     $-2
           mov     SPI1BUF,w2
           mov.b   w2,w1
           swap    w1

           mov     #0xff,w0
           call    send_w0
           bclr    SPI1STAT,#SPIROV
           btss    SPI1STAT,#SPIRBF
           bra     $-2
           mov     SPI1BUF,w2
           mov.b   w2,w1

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

;send CMD55 + argument<31:0> 00 00 00 00 + 65 (CRC)
;                            |RCA| xxxxx

do_cmd55:  mov     #cmd55,w0
           call    send_w0
           mov     #0x00,w0
           call    send_w0
           call    send_w0
           call    send_w0
           call    send_w0
           mov     #0x65,w0
           call    send_w0

           call    get_48_0
           btsc    flags,#initd
           bra     init_done

;send ACMD41 + argument<31:0> 40 00 00 00 + 00 (null CRC)
;                             |             77
;                         CCS |
;send ACMD41 + argument<31:0> 40 00100000 00 00 11
;69 0100000                        |
;   ||                             |
;   |HCS                           |
;   |                              |
;  busy          V range 3.3 - 3.4 |

do_acmd41: mov     #acmd41,w0
           call    send_w0
           mov     #0x40,w0                ;=3D 1, HC support
           call    send_w0
           mov     #0x00,w0                ;0x20 3.3V - 3.4V, CRC 61, 0x00=
=20
CRC 77
           call    send_w0
           call    send_w0
           call    send_w0
           mov     #0x77,w0                ;CRC
           call    send_w0

           call    get_48_0
           btss    flags,#initd
           bra     do_cmd55                ;loop until 0x00

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

init_done: bclr    SPI1STAT,#SPIEN         ;disable SPI module
           call    usec10
           mov     #0b0000000100110111,w0  ;change to high speed
;                                110                             2:1
;                                   11                           1:1 ->=20
16.94MHz (33.88/2)
;
;                                101                             3:1
;                                   11                           1:1 ->=20
11.29MHz (33.88/3)
;
;                                100                             4:1 ->=20
8.47MHz (33.88/4)
;                                   11                           1:1
           mov     w0,SPI1CON1

           call    usec100
           bset    SPI1STAT,#SPIEN
           call    usec100
           return

;some dsPIC SPI flags don't work - use delays

send_w0:   mov     w0,SPI1BUF              ;load data into SPI buffer
           call    usec50                  ;wait at 368.64kHz
           return

send_w0_f: mov     w0,SPI1BUF              ;load data into SPI buffer
           call    usec                    ;wait at high speed
           return=20

--=20
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