This is for the TIN version, the EING version will be listed as a separate item.

When the 8085 came out, it was a vast improvement from the 8080 in terms of the amount of support and glue logic it took just to make a minimum system. Intel really pushed the simplicity of the 8085 when utilizing other components in the MCS-85 family like the 8755 EPROM + I/O, the 8155 RAM + I/O, and the 8185 RAM. These components all used the ALE signal and internal address latching so they could be integrated with the 8085 without any glue logic or support chips.

Intel published this the minimum system design (8085, 8755, 8155) and even board layouts in their catalogs. This MCS-85+ is pretty much that same idea but since they are readily available, this design also includes intel's 8185 1K RAM, and that design shows up in the 8185 datasheet. The 8185 adds an additional 1K Byte of RAM to the board, but the board is fully operational with just the 256 bytes of RAM within the 8155.

The board has a TTL level serial port utilizing the SID / SOD lines from the 8155.

This is for the latest version, v1.1 of this board which has the following changes (please see user's manual for more information).

• Reconfigure 8156 TimerOut JP4 to remove RST7.5 and replace with TRAP for resident monitor single step
• Change serial connector J4 to 6-pin to include power and RTS/CTS
• Add switch SW2 on Supply +5V
• Add LED D3 on feed +5V (before switch)
• Remove bus status (S0 & S1) connector J6

Note: You will need to be able to program the 8755 EPROM, these are a few options:

• There is an arduino shield 8755 programmer on Matt Millman's site here. I have a few bare boards of Matt Millman's arduino shield programmers and his 8755 adapter listed here. I will list those bare boards (as a set) for sale simply for the convenience of anyone wanting this MCS-85+ minimum system. Any support for the boards will need to come from him. The design for these boards are on his website and most likely available from many other sources.
• Depending on my schedule and for a small fee, I may be able to program your 8755A with the current monitor I have ported to this board.
• I have some 8755A EPROMs that I will pre-program with the latest version of the resident monitor listed here.