Mini-08 Computer

Scott Baker, https://www.smbaker.com/

Description

The Mini-08 is a Single Board Computer (SBC) based on the Intel 8008 CPU, an 8-bit processor that was designed in approximately 1972. The Mini-08 has the following features

• 8008 CPU
• Up to 128 KB of RAM, mapped in 4K pages
• Up to 128 KB of ROM/EPROM/EEPROM, mapped in 4K pages
• On-board 8251 UART serial port
• 8 Onboard Diagnostic LEDs
• Support for interrupts
• A mostly-RC2014-compatible expansion bus connector

Also featured is an optional display board, which piggybacks on to the mini-08 and adds the following:

• Ten 7-segment hexadecimal display digits
• A 16-digit hexadecimal keypad
• Complex Sound Generator (3 music voices + 1 noise generator)
• Real-Time Clock

Note that the 4th digit from the right is intentionally blank in these examples in software. The display is showing a split-octal address (two groups of 3 digits) followed by an octal value (3 digits). All 10 displays are usable if you decided to use alternate software.

Alternate Display Board

In case the DM9368N drivers are hard to find or expensive, I have created a variant of the board that uses TIL311 integrated digits and drivers. They're also hard to find and also expensive!

The color of the backlit keys depends on the color of the LEDs you chose. In the TIL311 example, I went with red LEDs for the keys to have a matching look. The LEDs are at the bottom center of the keys, so the keys are a little bit unevenly lit.

Jumper Settings

CPU Board

Jumper	Position	Default	Description
SJ1	1-2	X	Two page registers (74HCT670) installed
	2-3		Only one page register installed
JP2, JP12	JP12-1		115200 Baud
	JP12-2		57600 Baud
	JP12-3		38400 Baud
	JP12-4		19200 Baud
	JP12-5		9600 Baud
	JP12-6		4800 Baud
	JP12-7		2400 Baud
	JP12-8		1200 Baud
	JP2-1		600 Baud
	JP2-2		300 Baud
	JP2-3		150 Baud
	JP2-4		75 Baud
JP4	1-2		CTS follows DSR
	2-3	X	CTS always on
JP5	1-2	X	MEMRD controlled by INTCON PLD
	2-3		MEMRD directly controlled via bus PLD
JP9	1-2	X	RTS is RTS
	2-3		RTS is DTR
JP10	1-2	X	RC2014-A8 is A12
	2-3		RC2014-A8 is GND
JP11	1-2	X	Power-on CPUINT controlled by INTCON PLD
	2-3		INTCON PLD bypassed, CPUINT directly controlled by POR
JP13		Present	Enable 8251 UART

Display Board

Jumper	Position	Default	Description
SJ1		Present	RTC-CS is GND
JP1		Present	Onboard speaker is enabled
JP2		Present	Enable keypad backlight
JP3	1-2	X	Front panel interrupt to INT pin
	2-3		Front panel interrupt to FPINT pin (RC2014-A14)

Ports

The following describes the IO ports that I have allocated to various peripherals.

Input

• 0 BB Serial / Dip Switches (internal)
• 1 Interrupt register (internal)
• 2 8251 UART - Data
• 3 8251 UART - Control
• 4 FP Keyboard
• 5 RTC
• 6
• 7

Output

• 8 BB Serial / LEDs (internal)
• 9
• A FPEI (internal)
• B FPDI (internal)
• C mmap (internal)
• D mmap (internal)
• E mmap (internal)
• F mmap (internal)
• 10 Port multiplexer / RTC-ALE
• 11 Sound
• 12 8251 UART - Data
• 13 8251 UART - Conrol
• 14
• 15 RTC
• 16
• 17
• 18 FP Digits 0-1
• 19 FP Digits 2-3
• 1A FP Digits 4-5
• 1B FP Digits 6-7
• 1C FP Digits 8-9
• 1D FP Dots 0-7
• 1E FP Blanks 0-7
• 1F FP Dots 8-9, Blanks 8-9

Note to self: 18-1F were the IO Mapper on the H8 board. Some of my code may still output stuff to those ports.