Re: Microcontroller selection

On Jun 27, 5:00 pm, Jim Granville <no.s...@xxxxxxxxxxxxxxxxxxxxxx>
wrote:
Ulf Samuelsson wrote:
"Ravishankar S" <ravishanka...@xxxxxxxxxxxx> skrev i meddelandet
news:f5tibc$9fb$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

thanks group, once again for the hints:

that narrows down my search, since there are a huge number of
microcontrollers out there.

linux: now it seems overkill for the application. that's now for sure..

AP7000 is not suitable: it has way too many peripherals..and its intended
for multimedia low-power apps, but AVR32UC - microcontrollers seems to be
a
perfect fit. Im yet to look at the ST micro.

If you want high speed USB (480 Mbps), your selection is limited.
If you accept Full Speed USB (12 Mbps), then your next
selection criteria should be high speed DMA driven synchronous
serial peripherals.

The Atmel synch serial port peripherals generally run as fast as the CPU
core.

Since you are targeting JTAG, I'd suggest a simple Compression wrapper
on the USB link. The JTAG clock data has to be uncompressed, but
you can stream the USB data compressed, and that will remove any USB
bottleneck. - and it is the long datastreams that will benefit the most
from compression.

It's not always so simple. I have an ARM chip with a slow Jtag/debug
wire. Fast USB datastreams would overrun the ARM state machine. I
have to slow down the USB side just to avoid overrunning the ARM
chip.


So, target a device with good DMA into largish RAM blocks, and with the
fastest possible SPI CLK speeds.
USB -> DMA -> Packed RAM
PackedRam => CPU Unpack => UnpackedRAM
UnpackedRAM -> DMA -> SPI/SSC

Ulf can probably help with the details :)

-jg


.

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