chip pinout help

From: Dwight K. Elvey <>
Date: Thu Aug 22 15:34:01 2002

>From: "Eric Smith" <>
>> Hmm, but then how is translation done on the inputs to the ROM? It is
>> a TTL device feeding the address, so the 0-5v swing (0.5v to 4+v)
>> swing would appear to be an input swing of +15 to +20.
>No translation required. PMOS thresholds are within a few volts of the
>positive rail.

 The only issue with PMOS is on the outputs. They
may not pull down as hard as a TTL input pulls up.
This is generally fixed with a pull down resistor
and/or a diode to limit the negative travel. Some
TTL can tolerate some negative on the input, most
CMOS can't ( I think the 4049 can though ).
Received on Thu Aug 22 2002 - 15:34:01 BST

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