Hi V8meathead
Several EPROM's are sometimes used in a system, this is why you find the pins /E and /G, the / means that they are active low (confirmed also by the small circle) and are used to (/E) enable a particular chip so that it can be read from or whilst programming, can be written to. The /G is an output enable. Normally all EPROM's will have their /G pins connected to 0v and the /E pin enabled individually so that data from only one chip will be output onto a common databus. This means that for every EPROM in this system every Q0 is joined together and all Q1's etc., forming a databus. Whilst the /E input is high (=1) data out is tristated or invisible.
Whilst there are many other ways of doing this, consider what would happen if you had programmed the bit pattern for a 7 segment LED as data in each of the lowest 16 addresses?
If you address location 0, the bit pattern could be used to show 0 on a display, location 1 would show 1 and so on...
It's also possible to program quite complex test sequences using a single EPROM, imagine a parallel counter which is attached to the address pins of the EPROM. At each clock transition, the address increases by 1 giving a different byte on the data output - that byte is then used to do something with other logic and can inhibit the clock until the system is ready for the next address.
Hope this helped
Ed
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