I am using the SPI port in my program for the ADSP21369,
and I also use FLG0 through FLG3 for diagnostic output. I have
found that when I try to write to the FLAGS register close to
where I use SPI communications in my program, the processor can hang.
It says in the manual that if you disable the SPI port by setting
a bit in the PMCTL register, you can't use the FLAGS because
they are "synchronized to the clock." I must admit that I have
no idea what that means. I don't write to the PMCTL
register at all, although I do disable the SPI port at various times,
by writing zeros to the SPI control registers. But still there seems
to be a definite interaction between using SPI and changing flags
by writing to the FLAGS register, and as I mentioned it can
crash the program. Does anyone understand the nature of this
interaction? Is it documented anywhere? I really don't understand
the brief allusions to it in the Hardware Reference Manual and
the Programmers Reference manual.