Hi,
Do you use 'volatile' type qualifier to prevent undesirable
transformations of FPGA registers reading code?
BR
Ilya
2011/8/1 andy_code <andy_code@xxxxxxxxxx>:
>
> hi,
>
> I have a function I wrote that part of a keypad reading interrupt for an
> embbed os we have written for coldfire processors
> in this function the code reads an FPGA that controls the interrupt, it
> should only read it once any more and
> it would confuse the FPGA.
>
> here is the original function
>
> void keypad_isr(void)
> {
> /* read a character from the key buffer */
> FPGA_UART_DATA *ptr;
> FPGA_UART_DATA kpd;
> int g;
> int n;
> KEYBUFFER *kb;
> char ch;
>
> kb = &key_buffer;
> asm(" halt"); /* just for debugging */
> ptr = FPGA_UART; /* make a pointer to the FPGA register */
> // read upto 8 keys from the keypad
> for( n = 0; n < 8 ; n++ )
> {
> kpd = *ptr; /* read from register (only do this ONCE) */
> g = kpd.fifo_cnt;
> if(g == 0)
> return;
> ch = (char) kpd.rx_data;
> kb->status = ch;
> if( ch != 0 && ch != -1 )
> {
> if ( kb->current_location >= MAX_KEY_BUFFERS_SIZE-1 )
> {
> kb->current_location = MAX_KEY_BUFFERS_SIZE-1;
> }
> kb->key_buff[kb->current_location] = ch;
> kb->current_location++;
> }
> }
> }
>
> ok now here is my problem, gcc does not use an address register for the
> pointer, and it insists on reading the FPGA directly twice ????
> here is generated assembly from gcc.
>
> keypad_isr:
> lea (-12,%sp),%sp
> movem.l #1036,(%sp)
> move.w -1073741664,%d0 <<<--- should use %a0 surely
> clr.l %d1
> move.w %d0,%d1 <<< --- theres the read
> moveq #13,%d2
> lsr.l %d2,%d1
> tst.b %d1
> jeq .L3
> moveq #8,%d1
> lea key_buffer+33,%a1
> lea key_buffer,%a0
> lea key_buffer+1,%a2
> jra .L5
> .L8:
> move.w -1073741664,%d0 <<< --- look its done it again ?????
> clr.l %d2
> move.w %d0,%d2 <<< --- ARRRGGGgg its knackered my FPGA
> moveq #13,%d3
> lsr.l %d3,%d2
> tst.b %d2
> jeq .L3
> .L5:
> move.b %d0,%d2
> move.b %d0,(%a1)
> move.l %d2,%d0
> addq.l #1,%d0
> and.l #255,%d0
> moveq #1,%d3
> cmp.l %d0,%d3
> jcc .L6
> clr.l %d0
> move.b (%a0),%d0
> move.b #30,%d3
> cmp.l %d0,%d3
> jcc .L7
> move.b #31,(%a0)
> .L7:
> move.b (%a0),%d0
> clr.l %d3
> move.b %d0,%d3
> move.b %d2,(%a2,%d3.l)
> addq.l #1,%d0
> move.b %d0,(%a0)
> .L6:
> subq.l #1,%d1
> jne .L8
> .L3:
> movem.l (%sp),#1036
> lea (12,%sp),%sp
> rts
>
> ok how do i stop this happening, thats not the code I wrote.
> please help, I is tearing my hair out
>
> thank you
> --
> View this message in context: http://old.nabble.com/gcc-4.6.1-messes-up-code----why-tp32169196p32169196.html
> Sent from the gcc - Help mailing list archive at Nabble.com.
>
>
