eprom size?

[steve ravet]

The cylinder select is specified by a voltage.  Here's a post from Ludis
explaining it.

---------------------------------------
I've just discovered how to select the number of cylinders in the P4 ECM
hardware.  The number of cylinders is selected by the voltage on pin 11
on the 34984 (aka 79435) chip.  This is U13 in a '727, '730, and '749. 
The pin 11 voltage comes from pin 56 of the MEMCAL.  This in turn
connects to pin 13 of the 16 pin resistor network in the MEMCAL.

Here's how the voltages are interpreted:
  0 to 1   volt  : 8 cylinder port injection
  1 to 2.5 volts : 6 cylinder port injection
  2.5 to 4 volts : 4 cylinder port injection
  4 to 5   volts : throttle body injection (any cylinder count)

The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
not driven (no MEMCAL).

The CPU can read out the pin 11 mode selection.  Code 41 will be flagged
if it doesn't match the cylinder selection stored separately in the
MEMCAL's EPROM.
------------------------------------------------------------------------

So you could plug it into an ECM and measure the voltage.

--steve

Daniel Collins wrote:
> 
> I have just been given some memcals that are supposed to be for a V8  ecu
> unfortunately my friends kids have taken all the id stickers off !!
> 
> Is there a quick way to verify the size of a memcal eprom and if they are in
> fact V8 memcals.
> 
> ----------------------------------------------------------------------------
> To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
> in the body of a message (not the subject) to majordomo at lists.diy-efi.org

-- 
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org