The RAM is battery backed using the DS1210 NVRAM controller (U8). The 62256 32 KiB SRAM (U4) is used for the system RAM. The MAX232A RS-232 driver/receiver (U7) is used to convert TTL logic levels to RS-232 voltage.
#Eprom programmer design 8085 serial#
The board uses the Intel 8251A USART (U2) for serial input / output, for example for connecting a console. The 74*573 octal latch (U6) is used to demultiplex the lower 8-bit of address and data bus. The MiniMax8085 is based on the Intel 8085A CPU (U1). PCB Layout - Version 1.0 Design Description Hardware Documentation Schematic and PCB Layout 40-pin extension bus connector, including most of 8085 signals and demultiplexed data and address buses.EEPROM, UV EPROM or Flash ROM memory is supported 82C51A or 8251A USART for console connection.It reduces the number of components, allows for tweaking the configuration by re-programming the SPLD, and provides an introduction to the programmable logic devices. It uses a GAL16V8/ATF16V8 simple programmable logic device (SPLD) instead of discrete logic ICs for the address decode and the frequency divider for USART. The resulting design includes 8085 CPU, 8251 USART, 32 KiB SRAM, 32 KiB or 16 KiB ROM. Glitch Works 8085 project didn't have an on-board UART.NCB85v2 is a little bit too complicated for my needs.NCB85 was the closest, but it doesn't have an extension bus.
While I liked these projects, they didn't quite meet my project design goals: I checked the Internet for existing homebrew 8085 computers and found Roman Fülek's NCB85 and NCB85v2 projects, and Glitch Works 8085 projects. to include the memory and an input/output device, for example a UART) with an extension bus. I wanted the project to be simple to build, with a minimal number of components, but yet to be a fully functional single board computer (e.g. It looked like a good start for an 8085 based computer that can be used to teach my kids some computer design and programming basics. Among these ICs were there: an 8085 CPU, an 8155 RAM with I/O ports and timer, a couple of 8255 PPIs, an 8282 latch, and some 27C128 UV EPROMs.
#Eprom programmer design 8085 series#
In the spring of 2014 my kids and I visited a local surplus store, where my kids found some Intel 8000 series parts in the kids-fill-your-bucket area. The MiniMax8085 project has been brewing for almost three years. Frequently Asked Questions and Troubleshooting.Minimal 8085 Single Board Computer Table of Content