Re: Repairing a SFD-1001 (8250/LP, 8050, 4040, 3040, 2040)

From: Jim Brain <>
Date: Thu, 11 Aug 2011 21:46:36 -0500
Message-ID: <>
On 8/11/2011 8:26 AM, Hoffmann-Vetter, Martin wrote:
> Okay, the 2364 has one chip select signal. So you have two states: inverted
> or not.
That's the first part.  Yes, it is optionally inverted to handle 2364 
variants with CS instead of /CS
> Yes, but the 2332 has two chip select signals (see the datasheet
> or
> at
> page 2-17). You can programm it via mask, so any combination are possible
> (0: low aktiv, 1: high aktiv and 2: don't care). You can use both, only one
> or non chip select. And all used chip select can be inverted or not.
I accomplished this by using the /CE signal on the EPROM.  Both CS 
signals are routed to '86 units to optionally invert them, and then one 
is routed to EPROM /CE while the other is routed to /OE
> Or you use a 139 (open collector) with a pullup resistor. Now you can put
> one or more jumper and have a programmable wired or gate!
Can you clarify?  I understand '129 is not the IC, but even with a 
suitable IC, what are the instances where you would *NOT* want the 
decoding of all the CS lines on the 6540?

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Received on 2011-08-12 03:00:03

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