Hybrid Energy Data Logger

SAbus 68008 processor timeline

The bulk of the design was done in 1988 to generate a standard set of boards for automation. The software was written during 1988 and 1989. The data logger was supplied in 1990.

SAbus 68008 processor board top bottom layers

The top and bottom CPU PCB layers were scanned in from the documentation and combined with Photoshop. The top layer is red and the bottom layer is blue.

Specification

Processor Card

SAbus 68008 processor board

The processor was a 68008, (32-bit internal registers but 8-bit data bus) is shown on the right. This was made in 1988/89 and used the MC68901 peripheral chip for a serial port, some parallel I/O lines, counter and timer. This was an early board for prototyping and was only two layers. The card size was 220×100mm for the bus that South Africa tried to standardise on (SABUS).

Memory Card

SABUS memory card

The memory card shown here was designed in 1988 and is 16-bits wide, so was either partially populated or a different card was used to make up 512kBytes

64 Output Card

SABUS latch card

The output card used ’273 type latches, which are reset on power-up. They sink 24mA each with external transistor cards to drive relays or higher loads. The data bus was 8-bit wide. The boards were sold for less than $100.

64 Input Card

SABUS Input Layout

The input card used ’245 type buffers. External card performed signal conditioning for maximum input voltage of 5V at this card. The data bus was 8-bit wide. The boards were sold for less than $100.

Backplane

SABUS backplane Layout

One side of the 7-slot backplane. Simple two sided construction with ground plane between signals. About a tenth the price of VME boards (certainly not as high spec). Based on SABUS. On the left-hand side, a position was available to plug a board into the back of a rack without using an extender board. Was also used for debug—scope trigger and single step hardware. The backplane was about $70.