What is it?

An 8085 CPU Module designed for the RC2014 computer system. It provides a 8085 CPU operating at nominally 7.3728MHz, integrated with the RC2014 Z80 Backplane. It is a 4 layer PCB.

Why did you make it?

To support RC2014 standard modules while using the 8085 CPU. Adaption of the Intel 8085 bus signalling to the Zilog Z80 standard is included.

What makes it special?

The 8085 CPU Module is fully buffered from the Z80 bus using (preferred) AHCT logic. This has better drive characteristics than the CPU itself, and this potentially reduces ground bounce when using the standard RC2014 CF Module.

Includes DS1233 based power monitor and RESET manager circuit, to provide a clean RESET signal and ensure sufficient voltage is available before releasing RESET.

An adaption circuit is provided to match the 8085 bus signals to the Z80 /IORQ signal expected by RC2014 standard modules.

A Wait State circuit is provided to match the 8085 READY signal timing to the Z80 /WAIT signal expected by the RC2014 standard modules such as the APU Module, and the UX Module.

Both Digital Research CP/M-IDE 2.2 and Microsoft Basic 4.7c are supported by this 8085 Module.

Provided software solutions work with either the RC2014 ACIA Serial Module, or with the Tynmouth 68B50 Clocked Serial Module for RC2014. Both the APU Module and Memory Module are optional but useful additions to a 8085 CPU system.

CPU Options

Recently I purchased some second source 8085 CPUs, and an additional Intel OEM option to test. It is very gratifying that all of the selected second source CPUs function correctly, with just one exception. See attached image.

Testing was done with a minimal RC2014 System consisting of a Backplane 8 equipped with an ACIA Serial Module, a CF Module Version 2, a Memory Module, and an 8085 CPU Module. To get an approximate base line current requirement the CPU was unplugged and the remaining power requirements were measured, and from this it is clear which devices are implemented in NMOS, and which in CMOS. Only the OKI and Tundra devices seem to be CMOS based.

Ordering Options

This is the 8085 CPU Module Printed Circuit Board (PCB) Only.

If the postage is too high, then please use the attached documentation to make your own, and share with others.