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Still problem with SPI Interrupt

Donghua Gu

Using Atmel AT89C51CC03, and having very strange problem with SPI. My interrupt routine is like this:

void SPIISR(void) interrupt 10
{
        if (SPSCR == 0x88) {P1_0 = ~P1_0;}
        tmpchar = SPDAT;
        SPDAT = 0xCC;
        P1_1 = ~P1_1;
}

It took me lots of time to narrow down SPSCR to 0x88, but with this code, what I see on the scope is that P1_0 toggles every 16~17 us even when chip select is HIGH. After the first low chip select, P1_0 stops toggling, and P1_0 never toggles again. P1_1 never toggles at all.

So I am really confused here. P1_0 is toggling and P1_1 is not. Does it toggle from the interrupt? Why does this only happen before first LOW Chip Select and nothing during LOW Chip Select?

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