RAMCAL design options

[Andrew K. Mattei]

Ludis Langens wrote:
> 
> Several of you expressed interest in a MEMCAL with ECM writeable RAM.
> I'm calling this a RAMCAL.  See a previous message for an architectural
> overview of how custom software in the ECM could write to RAM without a
> ~WE signal. 

I like the idea, but have a few questions for you. :)

OK, first off.. My assumption on the theory of operation. We would
actually be using the ECM to write to SRAM. The way this would work
would be that we use a RS232->TTL converter on a computer (laptop) to
send messages in to the ALDL data port. We would have a subroutine
inside the ECM RAMCAL that picks up on this "special" datastream, and
writes the data to the SRAM memory via utilization of the !CS and !OE
pins (I *assume* these aren't hardwired +/- in the ECM, and are
available for our usage). Our message to the ECM would consist of a
special activating function code, then the address, then the data? Also
a Chip Select function code? (just thinking out loud)... Also, thinking
about the boot up sequence... When you plug the ECM in, is the
"existing" EPROM copied in to our SRAM, and then the computer reads from
our SRAM, or is it the ECM starts up reading the EPROM, and then when
given the command it jumps to reading the SRAM?

OK, I there's a couple of my assumptions on how it would work. So, now,
on to which ECM's it would work on (our "market"). I don't know if it
would work on my 165 - I honestly don't know if that ECM is 8192 or 160
PWM based. I'm "guessing" that it's 8192. So, sounds like it would work
for my application. However, it would not work on a 160 PWM datastream -
older ECM's, right? They would be forced to use a more conventional
emulator.

We do need some things to kick this off... Modify the EPROM in the
MEMCAL to support the jumping / decoding, software to download the
changed parameters to the ECM, and hardware/software to compile and
program the Xilinx chip.

When I get some time, I plan on going to the Xilinx web page and getting
more information on this IC. I like figuring it all out. :) My son and I
will bat this around some hopefully this weekend... I'll change his
diaper and talk to him about it. ;)

Gotta start 'em early - he already likes the air tools!

-Andrew