FPGA Central

Hi

I would like to do a DMA to external memory from an ADSP 21160M using all 64
bits of the External Port (ie. nWrh and nWrl should be asserted together).
I'm running the EP in asynchronous mode and have set bit 5 of the DMAC
register to '0' (to select 32/64 bit data type) and bits 8-6 to "000" (to
select no packing). However, only the nWrh strobe seems to be asserted. I
don't know whether the DSP is capable of doing 64 bit DMA to external
memory, but I can make it do 64 bit reads and writes using the LW mnemonic,
as shown in the example below:

dm(0x20800010)=r14(LW);

(This is despite the following text on pg 5-45 of the Hardware Reference:
"External memory space accesses using Normal word addressing and the LW
mnemonic perform a 32-bit accesses, not a 64-bit access.")

The following text on page 5-46 is rather discouraging...
"When looking at Table 5-8, it is important to note that Long and Short word
addressing may not target multiprocessor memory space or external memory
space."

However, I suspect that it just might be possible to do 64 bit DMA's... I
just can't figure out how!

Any help is much appreciated.

Many thanks

Sam

--

"Sam Duncan" <[email protected]> wrote in message
news:brps1m$5goua$[email protected]..
> Hi
>
> I would like to do a DMA to external memory from an ADSP 21160M using all
64
> bits of the External Port (ie. nWrh and nWrl should be asserted together).
> I'm running the EP in asynchronous mode and have set bit 5 of the DMAC
> register to '0' (to select 32/64 bit data type) and bits 8-6 to "000" (to
> select no packing). However, only the nWrh strobe seems to be asserted.
I
> don't know whether the DSP is capable of doing 64 bit DMA to external
> memory, but I can make it do 64 bit reads and writes using the LW
mnemonic,
> as shown in the example below:
>
> dm(0x20800010)=r14(LW);
>
> (This is despite the following text on pg 5-45 of the Hardware Reference:
> "External memory space accesses using Normal word addressing and the LW
> mnemonic perform a 32-bit accesses, not a 64-bit access.")
>
> The following text on page 5-46 is rather discouraging...
> "When looking at Table 5-8, it is important to note that Long and Short
word
> addressing may not target multiprocessor memory space or external memory
> space."
>
> However, I suspect that it just might be possible to do 64 bit DMA's... I
> just can't figure out how!

I'll have to go back to user manual to provide anything useful (and
detailed) for you.
However, I vaguely remember burst mode DMA being able to do 64 bit writes
for sure (can't remember if this can be done with other modes).

Cheers
Bhaskar

>
> Any help is much appreciated.
>
> Many thanks
>
> Sam
>
> --
>
>
>