Using SRAM for an Apple II

I just read UncleBernie's response here: 


So, I figured the timing was right to discuss the issue of SRAM write timing on an Apple II.


What I believe that UncleBernie is describing is a problem whereby if you synchronize the write with the fall of Phi2 that it is too late.  The address and/or data is now corrupted, on the busses, and the data written will be bad.  There is a similar problem, on Atari computers, due to the buffering of Phi2.  I am also thinking the data bus corruption issue may be made worse because after Phi2 falls, the address and data busses are now used by the video subsystem so the additional hold time of the CPU is effectively eliminated.


I was looking into using SRAM and was thinking that it may be possible to use SRAM if the SRAM's write enable signal is high on read and low when the CPU R/W is low and /CAS is low.  This would result in the SRAM write enable going high when /CAS goes high...which should result in the data being written before Phi2 falls and the busses are corrupted.


This chart shows why you wouldn't want to use Phi0 or Phi2 to synchronize the write timing:



Character Generator Tester

Last year I developed an ASCII Keyboard Tester (see and to please my curiosity in the electronic workings of the Apple-1. Great to see this scene of enthusiasts is so alive.

I came across an article by Don Lancaster in the Popular Electronics April 1974 issue about the ASCII Keyboard and Encoder. They use a Monsanto MAN-2 display, a 5x7 dot matrix. Using a 2513 character generator, it displays a single character that is typed in on the ASCII Keyboard. It is on page 29/30, some PDFs around there are missing these specific pages, so I attached the article here for reference.

Anyway long story short, I designed a Character Generator Tester, which shows the characters that are generated by the 2513. I use a KingBright TA-07-11EWA as a display. It also supports 2316B, 2716 EPROM and 2816 EEPROMs. So it enables you to test Character Generator’s for the Apple-1 and Apple ][, and you can test self made EEPROMS (or 2513 drop-in’s) that should replace the originals.


Non-Contact Voltage Testers Comparison Review (Fluke, Ideal, Craftsman, Kaiweets)

I suspect most people on Applefritter have used a non-contact voltage tester. They're the sort of thing my mom likes to put in Christmas stockings, so I've ended up with several. There's a lot more differences between them than I would have expected, hence this review.

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