MCUs other than ARMs

Ulf Samuelsson wrote:
> rickman wrote:
> > Ulf Samuelsson wrote:
> >>> There are MCUs out there that have 3 SPI ports, so it would be
> >>> redundant to use a CPLD.
> >> ...
> >>>  It would have been nice to use an ARM as we just recently started
> >>> moving our designs away from 8 bit MCUs to ARM devices.
> >>> But I have serious power constraints and the
> >>> ARMs with 3 SPI ports use way too much power.
> >>
> >> AT91SAM7A3 draws too much power?
> >
> > At 200 mW, yes, I think that is more power than I can afford.  Of
> > course we can use techniques to reduce that when the CPU is idle, but
> > I don't like to start with more than a 50% figure unless I *know* the
> > CPU loading up front.  With the CPU using 100% more than the total
> > board power budget, I don't think I can work with that.
> >
> > How certain are you that the SSC will work in SPI slave mode.  Is
> > there an app note on this?  The SPI speed is very slow at 100 kbps.
>
> The SSC is not an SPI, it is a shift register which can work in master or
> slave mode.
> In the slave mode, you have a clock input, and in promiscuous mode
> the SSC will shift in everything which is clocked.
> In other modes, it will read n bits, m clocks after the start of a
> framesync.
> The SSC has slave  DMA support which the SPI doesn't have.
>
> A good programmer can use his master SPI to communicate
> with the SSC.

What if our "good" programmers are busy?  Can an average programmer
make it work?  Is there an app note?  To be honest, I get tired of
trying to figure out how to use parts in new ways when what I need is a
different part.  The SAM7X was the part originally slated for this
socket.  I can get a part from Freescale with three SPI ports, but that
would be anew processor for this group.

I can ask the local FAE.


> On the Power issue, you can of course run the part at lower clock frequency
> to get what you want, the SAM7X also has dual SPI and SSC.

I would like to consider that, but I don't see in the data sheet where
they give enough info to estimate the power at any speed other than
max.  What would it take to get power consumption at slower clock
speeds, like 13 MHz perhaps?

rickman wrote:

> I don't have hard requirements yet, but I think 128 kB of Flash will do
> the job along with 16 kB of SRAM.  I may need an I2C port and of course
> a number of I/O pins (yes, we still have to guess, but 30 should do the
> job).

There is a parametric search service for ARM based MCUs from all major
chip vendors at: www.sevensandnines.com/chipselector
A quick search showed that ST's STR730 series meets your requirements
for SPI's, I2C and memory. 

Rg, Tomas

Tomas wrote:
> rickman wrote:
>
> > I don't have hard requirements yet, but I think 128 kB of Flash will do
> > the job along with 16 kB of SRAM.  I may need an I2C port and of course
> > a number of I/O pins (yes, we still have to guess, but 30 should do the
> > job).
>
> There is a parametric search service for ARM based MCUs from all major
> chip vendors at: www.sevensandnines.com/chipselector
> A quick search showed that ST's STR730 series meets your requirements
> for SPI's, I2C and memory.

Thanks.  I am aware of the ST micro devices.  They are rather high
power though.  Pretty much all the ARM processors other than the Atmel
and Philips parts are twice as high as my board level requirement.  So
it is unlikely that I can get the power level low enough even using SW
features of power control.

I found a part that seems to be a UART interface that provides a slave
SPI interface.  I need to read the data sheet in detail to make sure it
will do what I need.  But it seems to allow me to convert an MCU serial
port to an SPI slave port.

"rickman" <gnuarm@gmail.com> wrote in message 
news:1160925517.042382.94600@b28g2000cwb.googlegroups.com...
> Ulf Samuelsson wrote:
> So the major requirement is 3 slave SPI ports.  The secondary
> requirement is low power, with 100 mW a target (along with lower power
> at lower speed or duty cycle).  The rest is negotialble.
>
> Anyone work with a 3 SPI device?
>

Renesas M16C62P series, like M30624 have 2 SPI and 3 UART/ SPI/ I2C.
Available from Digikey.

r.