Sinclair ZX80 / ZX81 / Z88 Forums

Depends on which version of the AT28C64 is used. One version has pin 1 as a no connect, the other version has an open drain RDY/BUSY (Ready/Busy) output.

Microchip / Atmel datasheet here.

Looks like Microchip have the older Atmel datasheet on their site! And that the version with the RDY/BUSY was dropped at some time.

A rebranded Microchip current datasheet is here. This has pin 1 as a no connect.

Mark

The data sheet I pointed to has it as NC and to further complicate it that first data sheet in your link as it as RDY/BUSY (or NC)
Surely it cannot be both?

No, can't be both.

Nice of Atmel to make it rather confusing

Anyway, if we take the Microchip branded datasheet as being the current version, all new chips will have pin 1 as NC.

Mark

On that we are in Bon Accord.