Beta

Beta computer

Original articles on the Beta appeared in 1984 in the popular-scientific magazine Kijk (which means ‘Look’ or ‘Watch’).
Design and articles by Steven Bolt, Pitronics. All rights reserved, this publication by permission of Mr Bolt.

Beta computer

The Beta computer is a small but fully functional 6502 system. Ideal for controlling applications! The base, called ‘controller’, is a PCB with 6502 cpu, a 6532 RIOT and a 2716 EPROM. A really minimal 6502 system with lots of I/O and a minimal IC count. This standard controller is meant to be inserted in a PCB called ‘terminal’ on which specific hardware can be placed, depending on the application.

Two ‘terminals’ have been described in the original articles, one acting as a development system, with KIM-1 like seven segment LED display, hex keyboard and an EPROM programmer. The second ‘terminal is a smaller board with a relay to switch a load and temperature sensor and also a keyboard and LED display. Besides the original articles, scanned and in dutch, the most relevant information of this system is shown in english, including source of the monitor.
Downloads:

The Robot Arm

On this page you can see the Beta computer put to work. Controlling a robot arm is a job a 6502 based machine like the Beta can do very well.

betac_arm-s

Beta controller

A minimal system, 6502, 6532 RIOT for I/O, timer and 128 byte RAM (zero page, stack, program memory, mapped all from address 0000) and a 2716 EPROM for a control program like the Beta monitor.

Beta computer

Beta computer

As you can see, a minimal system. To make it as universal as possible this controller needs an external clock, a Reset circuit and a power supply to start.

Terminal for development

The development system for the beta monitor has a hexadecimal keyboard , six hex digit LED displays, keys for A(ddress), D(ata), G(o)and a Reset key.

After resetting the Beta with the Reset key and pressing G the Beta monitor is atarted. With the A and D keys (with LEDs showing the current A or D choice) and the hexadecimal keyboard, addresss and data can be selected and dsiplayed and data stored. With the G(o) key a program at the selected address is started.

The memory map 6532 RIOT
0000 monitorvariables Data Register A 0080
0007 vectors (IRQ, NMI) Data Direction Register A 0081
000B variables EPROM, BRK Data Direction Register B 0082
0015 free RAM Data Direction Register B 0083
0077
0078 stack Port A7 rise/fall detection
007F
0080 I/O, timer 6532 Port A7 interrupt enabled on rise/fall 0087/0086
009F Port A7 interrupt disabled on rise/fall 0085/0084
F800 monitor Timer interruput/enabled/disabled
F9DF IRQ vector
F9E2 Breakpoint routine 1 009C/0094
FA39 EPROM routine 8 009D0095
FB7A NMI routine 64 009E/0096
FB7D 24 hour clock/alarm 1024 009F/0097
FFC5 character table
FFFA vectors 6502

Start addresses of subprograms

beta monitor

Beta monitor F9BF
Read EPROM FAC9
EPROM empty check FAE3
Write EPROM FB1B
24 hour clock/alarm FBEF

Source and binary of the Beta monitor:  Beta Monitor, source, and binary

The Robot Arm

beta computer

beta computer

beta computer

beta computer

Connectors

beta computer

Terminal as Temperature controller

This variant of the terminal shows how the Beta controller can be used to measure temperature and switch a device like a central heating system.
The difference with the development system are no EPROM programmer, a temperature controlled oscillator connected to PA7 and a relay. Also no crystal based clock, and a 50 HZ line frquency based interrupt at the NMI input.

beta computer

beta computer

beta computer