[Re: Using 28F256 in a 747 instead of 2732A??????????]

[Ludis Langens]

Dig wrote:
> 
> The real tragedy is that the '749 doesn't have a WE to the MEMCAL that
> I know of (anybody got a MEMCAL pinout?). You could proably pull one
> from the bus somewhere (off the slide connector terminals?) and run it
> to one of the unused pins on the end with the ESC substrate.

There's no ~WE on the MEMCAL.  There is a R/~W on the edge card.  In the
727/730/749, there are three unpopulated chip locations meant to add
2Kbytes of SRAM.  One of the chips is glue logic that generates ~OE and
~WE from the MPU's E and R/~W.

> I need to look at the CS on the EPROM on the 749... see if it toggles
> with chip accesses or whether they just pulled it low.

~CS is pulled low via a resistor.  The MPU controls ~OE.  Unless I
remember wrong, for each EPROM access it pulses low for 3/4 of an E cycle.

You might want to take a look at the (unfinished) schematics of the
1227748 ECM on my web pages.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/

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