On 5/14/2012 12:34 PM, Gerrit Heitsch wrote: > > With a CMOS-EPROM it's not much, but there are still a few NMOS-EPROMs > around that could get used and with them it makes a difference, at > least in heat output. > I would never recommend power hungry NMOS EPROM in a replacement. > > >> * I was worried that the delay of enabling the ROM and it's output >> drivers would cause timing issues. On a 250nS 27C64, it can take up >> to 350nS from !CE to data valid. That's compared to 120nS for !OE to >> data valid. > > Where did you get the 350ns for a 250ns EPROM? I'm looking at the > datasheet for a 27C64 from NS and that one states that for a 250ns > type, tCE (_CE to output delay) is 250ns and 350ns for a 27C64-350. > In that datasheet the times are supplied in a table and can be > misread. Since you mentioned 120ns (which is tOE for the 27C64-350, > the 27C64-250 has a tOE of 70ns), you might want to take another look > at that datasheet you used. Sorry, I mean 350nS 27C64 above. You are correct that 250nS has 250 and 70. > > >> If folks are sure the two can be tied together, please let me know. > > I have done it and didn't get any complaints from the circuits I used > that in yet, namely 1541 and C64. Well, that's nice, but hardly an exhaustive set of tests. > > Gerrit > > Jim Message was sent through the cbm-hackers mailing listReceived on 2012-05-14 19:00:22
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