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Z80SBCRC, Z80 single board computer for RC2014
This project started off as a quicky prototype to check out whether the lot of Z80 I purchased off eBay really can run at 20MHz (yes, they can). Because it is simple and fast, it is ideal as a single board computer in the small RC2014 form factor. Here are features of Z80SBCRC:
- Z80 running at 20MHz
- Battery-backed 512K RAM
- 32 banks, each bank is 16KB
- Simple serial port with serial bootstrap capability
- Serial port operates at 115200 N81, no handshakes
- Compact flash interface
- CP/M 2.2 and CP/M 3
- 100mm x 50mm pc board
- RC2014 bus interface
The heart of the SBC is a 5V CPLD, Altera EPM7128S, that implements the serial port, generates baud clock, interfaces to compact flash, and divides memory into 32 banks. The design has no ROM. The traditional ROM software are stored in battery-backed RAM. The serial bootstrap function loads the ROM-equivalent software into RAM when the board is powered up the first time; the system boots off the software in RAM for subsequent power cycles or resets. The ROM-equivalent software are protected by switching to banks inaccessible to normal software.