Due to the deregulation of the telephone industry, our client had successfully reverse-engineered many of the cards originally produced by Western Electric for a SLC-96 T1 telephone system. However, several cards were extremely difficult to reverse engineer as they had many full-custom ICs, including a microprocessor, EPROM memory, and a pair of gate arrays with over 10,000 gates each.
Additional requirements existed, including extreme temperature range, reduced power, high reliability, and low cost of manufacturing. Four different cards were required. The client required that no custom ICs be used in the resulting design, and all components had to be second-sourced.
MTSI first developed a disassembler for the processor code. By using a split screen editor, over 6,000 bytes of code were translated into the target 68000 computer language.
During this development, a design flaw in the CMOS 68000 microprocessor was found and reported to the manufacturer. Mask changes had to be made by Hitachi to eliminate the problem. The hardware was examined using logic analyzers, a computer aided engineering workstation, and other tools. Simulated circuits were tested against the known good circuits and modifications made. Seventeen full-custom IC’s were reverse engineered in this way.
A SLC-96 emulator was also developed. Controlled by a PC, this emulator allowed worst case timing changes to be incorporated in the design, and it reduced the need for the expensive and often unavailable pair of SLC-96 systems. A gate array emulator was developed and prototyped using wire-wrap technology. After testing of the original card, four gate array emulators were built and tested. The design was then extensively simulated and a gate array produced that matched the functions required.
Altogether, 23 emulators were built and tested individually and together. By using PLD technology, power was reduced, the need for full-custom circuit was eliminated, and the design was rapidly developed and tested.
All four cards are now in volume production. the gate array was found to be 100% correct after the first pass. All of the projects came in under budget and on time.