As a follow-up, I don't recall what chip you're using, but I recently
found an errata on the PIC24HJ256GP610A about SPI. I have code that
currently works on the non-A version, but does not work on the A version.
Trying to chase that down...

Harold

> Hi all,
>
> MChip Support have offered this as a resolution. I need
> a C to assembler translation in case I missed something
>
> ------------
> I wrote a small piece of code in C for SPI2 as follow:
> UINT8 writeSPI2( UINT8 value )
> {
>     SPI2BUF =3D value;    // write to buffer for TX
>     while(!SPI2STATbits.SPIRBF); // complete transfer wait
>     return SPI2BUF;        // read the received value
> and this is always working without any SPIROV issue.
> -----------
>
> Below is typical code I use to send a CMD to an SDHC card. In
> it, SPIROV must be cleared right before the buffer read or it
> simply doesn't work. Program will not get past the full buffer test
>
> How is MChip's code different ? I notice he uses SPI2 used for
> some reason - the dsPIC I have has only SPI1. He didn't say
> which PIC he's got his code running on
>
> If I execute this loop, which I think corresponds to the proposed
> solution,
>
> t_loop:    mov     #cmd00,w0               ;0 + 0x40
>            mov     w0,SPI1BUF
>            btss    SPI1STAT,#SPIRBF
>            bra     $-2
>            mov     SPI1BUF,w2
>
>            mov     #0xff,w0
>            mov     w0,SPI1BUF
>            btss    SPI1STAT,#SPIRBF
>            bra     $-2
>            mov     SPI1BUF,w2
>
>            bra     t_loop
>
> all that results is 1/2 an iteration (attached). Flow halts at the very
> first SPIRBF test. So his solution isn't appropriate for the dsPIC
> I'm asking about. And I've already told him about that loop above.
> He's just written in C and told me it works
>
> Please, if you can, consider the code carefully. I'm I wrong ?
>
> Joe
>
> Typical send CMD code
>
>            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
>
> ...more code
>
> send_w0:   mov     w0,SPI1BUF              ;load data into SPI buffer
>            call    usec50                  ;wait at 368.64kHz
>            return--
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>


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