SIGCD: Digital and Analogue Circuit Design

There were originally two SIGs covering Digital and Analogue Circuits. They were merged with the focus on supporting software for:

• Interactive small circuit analysis and design
• Large system analysis
• Microwave engineering (transmission lines, microstrips, etc)
• Interactive pre- and post-processing
• System modelling and simulation (analogue and digital)
• Establishment of a library of device and material characteristics
• Digital system specification
• Synthesis
• Simulation and fault analysis
• Testing and test generation
• Transient analysis of digital structures
• IC design and layout
• PCB design and layout
• Guidance and implementation aids for microprocessors
• Database system

The SIG mounted the following programs:

A library of microprocessor software including cross-assemblers, simulators was set up on the UMIST DEC-10.

ISPS

This package provided interactive simulation of a digital system described in the language ISPS, which is the computer implementation of the Instruction Set Processor (ISP) language. This allowed a digital system (of which digital computers are a subset) to be described at the register transfer level or at the programming level. The ISPS language was designed to describe digital systems. The ISPS simulator was designed to allow the user to set break points and interrogate the status of hardware at any point during the simulation. The simulator could also be used to initiate separate processes, which could be complete ISPS descriptions, and hence simulate concurrent systems. 20 ISPS descriptions of popular computer architectures could be used to create simulators which could execute code for the target machine. Special purpose cross-assemblers were developed for four popular 8-bit microprocessors: 8085, 6502, 6800 and 680l that could produce code in a form suitable for direct entry into the corresponding ISPS based simulators.

DDL and DDLSIM

DDL was a block structured register transfer language specially designed for describing digital hardware. It could handle combinational and sequential circuits.

DDLSIM could be used to simulate a large class of digital systems from register transfer descriptions to combinational networks.

Pre-processors were provided to make it easier to set up the input data for both DDL and DDLSIM.

DIGSIM

A suite of interactive programs that allowed the user to prepare data for the main batch mode logic simulation program, and to display graphically the resulting network. After the rigorous statistical simulation had been completed, the results could be analysed by interactive post-processing. The simulator handled real components stored in a library (flip-flops, shift registers, monostables and code converters, as well as conventional logic gates).

Some of the projects that used the software were:

Support for the SIG was provided by Pete Dewar, Ian Benest, John McLean and Robert Gay.

Extra Mural Development Contracts with Essex and Reading Universities assisted in the availability of software.

A Prime 750 was installed at RAL to run GAELIC in support of M.Sc courses in integrated circuit design at several British Universities (Edinburgh, Durham, Southampton, Brunel and UMIST).

The SIG was eventually merged with a parallel activity promoted by the Solid State Devices Subcommittee of SERC on design, placement and layout for digital ICs. Later still, all of the programmes in IC design became the responsibility of the Microfabrication Facilities Sub-committee of the Information Engineering Committee (IEC).