[comp.sys.next] image 2 of DSP external RAM

apte@portia.Stanford.EDU (R Apte) (12/13/89)

The array processing library seems to want to handle complex numbers
by storing all the real values and then all in the imaginary values
in flat external memory space.  This approach is fine unless you want to
use any of the features of the 56000, in which case you are in trouble.
Motorola defines an X and Y memory space for real and imaginary numbers
so that one address accesses an entire complex number.  Next seems to want
to support this mode but hasn't documented how to set the registers in
port c of the DSP to do this.  In appendix H of the manual there are 
a few comments to the effect that when A15 is high that X/Y~ is connected
to A12, thus making 4k complex RAM out of 8k real RAM.  Has anybody seen
this work?

raj b apte