This is a project I made a some years ago, a Z80 computer system. The “core” is functional, however, due to the lack of free time, other projects, and the old source code that I don’t seem to find anymore (must search old backups), some features are not yet functional and I don’t know when they will be. What is not working: VGA output, RTC, SD CARD, PS/2.
Firstly, I would like to say thanks to Thomas Scherrer, from http://z80.info/ . A great site with a lot of great info about Z80 systems, code, schematics, datasheets and so on. You can basically have no ideea about what a Z80 CPU is, and make a functional system (HW and SW) just by reading what’s on z80.info .
A small description of the system:
-Z84 CPU clocked at 3.57MHz , with a secondary oscillator to overclock the CPU to 8MHz (and yes, it works)
-32KB of ROM memory, 27C512 EPROM, half used
-32KB of RAM memory, M48Z25-70, Zero Power RAM, with internal Lithium battery
-2×16 LCD with backlight, HD44780 compatible controller (KS0066)
-6 8bit parallel ports, by using two 82C55 Programmable Peripheral Interface chips
-RS232, by using 16C550 UART + MAX232 level shifter
-RTC 72421 with battery back-up
-ISA port for ISA Video CARD. Missing “glue” logic.
Some pictures during the construction:
The inductor under the LCD is for a 5V switching mode power supply, used for the LCD backlight. The LCD that I used in this system wants a LOT of power for the backlight, it was killing the main linear regulator (the 7805 upper right, with a radiator attached).
Schematic in Eagle format can be found at:
Some useful datasheets:
Updates to come!