On 13/07/2016 8:48 PM, Gerrit Heitsch wrote: > On 07/13/2016 01:40 PM, smf wrote: >> On 12/07/2016 17:59, Jim Brain wrote: >>> >>> I think I tied OE to the 2364 select line, so if your use case uses >>> CE, you'll have to cut a trace, and if it uses both, then you're into >>> an OR gate, which my design does not support. >>> >> >> I'd have thought 2364 pin 20 (_CE) would make more sense to be connected >> to 2764 pin 20 (_CE). This would cover the case for _OE being grounded >> as well as when _CE & _OE are tied together. > > In man circuits they control the EPROM through _OE and tie _CE to GND > since that allows you to get away with slower EPROMs. This way the > EPROM is always aktive and decoding addresses, just the output buffers > are disabled. So you can hide quite a bit of the access time inside > the delay for the decoder that selects the EPROM. Downside: higher > power consumption with the old NMOS types. Doesn't really matter with > CMOS. > > > > If _CE & _OE are >> independently controlled then you probably ought to add a hex buffer >> with _OE1 and _OE2 and feed _CE and _OE to it. > > A simple OR gate (74LS32 for example) will tie _OE and _CE together > and produce the correct signal for a 2364. > I usually construct a simple OR gate using diodes and a resistor. Hasn't failed me yet. Message was sent through the cbm-hackers mailing listReceived on 2016-07-13 22:00:25
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