Reply by Hew How Chee ●June 30, 20002000-06-30
Hi,

We are in the process of upgrading our DSP from C549 to C5409 and have
a few questions that we need to sort out first before starting the
design.

i) Can the 5409 DMA transfer data from external memory between 8000h
to FFFFh to the McBSP serial port (tx and rx) ? The data sheet (SPRS082C
Apr 1999 pg 25) says that it cannot transfer from external memory to
peripheral or vice versa. However it also says that 2 channel is available
for
external accesses. So it is really possible ? If not is there any other way
to
DMA from external memory to the McBSP ?

ii) If the McBSP is connected to a 128 time slot PCM bus (shared
between another DSP), can I transmit more than 32 time slot and put the DX
pin
tri-state for the rest of the timeslot ? The datasheet says that it
can transmit max 32 time slot only (pg. 20) Can I set the frame length
(XFRLEN1) to 64 so that the DX pin is driven from time slot 0 to
timeslot 63 and go tri-state for timeslot 64 to timeslot 127 ? I don't
intend to
use the MCR registers since it is very troublesome.

iii) Is it possible to transmit starting from timeslot 64 up to
timeslot 127 >without CPU intervention to the PCM bus ? The DX pin should
not be
driven from timeslot 0 to timeslot 63. Once again usage of MCR is not
preferred.

Regards,
Hew