[Mark1960]

For the 4002 the -1 and -2 are two different address options, hardwired in the 4002.

The 4201 includes a single step circuit for the 4040, I don’t think the 4004 supported single step.

The 4004 was originally intended for use with the 4001 mask rom, but there were also a couple of chips to allow use with standard memory, i forget the part number of this pair of chips, but there was a later 4289 that combined these into a single 40 pin dip to interface to 1702 or 2101/5101 ram. The 4040 has a few additional instructions that support a modified harvard architecture via the 4289.

A few years ago I built up a 4040 system with 4289, using the single step feature of the 4201 and toggle switches to write to a battery backed 6264, kind of like a 4040 based scrumpi. I’ll try and dig out the schematic.