I’ve done several online searches for a complete MM5740 data sheet over the last several years. There is a version that can be found on many of the data sheet archive search engines, but it is missing at least one page, containing crucial information. I knew it was part of National’s MOS/LSI data book from the mid ’70s, but I couldn’t locate an online version of that book, and I really didn’t want to buy a physical copy. One of the key questions that couldn’t be answered with the existing online data sheet, is what exactly is the difference between the AAC/AAD/AAE/AAF versions.

Finally while exploring the possibility of using an AVR as a replacement decoder for the MM5740, I did another search and the data book turned up as a PDF at bitsavers.org. The last page of the data sheet show that the AAE version has N-key rollover and the AAF version has 2-key rollover. Otherwise they are the same. This means that the AAF version should be usable in the Apple/Datanetics keyboards, only with the loss of the n-key rollover feature. Also, in this data book are some app notes, that provide information on the AAC and AAD versions. Those versions decode the matrix differently, in order to make using an external PROM decoder simpler. They will not be compatible with Apple/Datanetics keyboards.

Once I figure out the best way to cut it out of the complete data book, I’ll put a copy of the complete MM5740 data sheet and associated app notes up on one of my web pages. For now, you can try to download the complete National MOS/LSI data book from bitsavers.org. Recently, I’ve have trouble accessing that site, but if you are persistant, you should be able to get through.