(UPDATE June 2022)

Fluke made many different versions of the 488 card over the 15 year production cycle. Some boards used a Z8611 4K MCU to provide the entire 488 function. Other later PCBs used a Z86E21F 8K MCU to interface to a uPD7210 LSI 488 bus controller. Sometimes this was a plastic OTP device, other times with a UV window. All PCBs with only one 40 pin DIP (Z8611 or Z8613) require a unique ROM for 8840A/AF and a different ROM for the 8842A. This is because the Fluke 8842A has an extended 20mv range, and it requires a different firmware set to access the extended range features.

All 488 PCBs that have 2-40 pin DIPs (Z86E21 & uPD7210) have enhanced firmware that detects which meter is is used in and operates accordingly.

The 488 bus command language is a rather simple set of 1, 2 or 3 character commands. In particular, the RANGE (Rx) and GET (Gx) commands are different in the 8840A & 8842A manuals.