Gate array or microcontroller? The engineers dilemma. A 4-bit microcontroller replacement case study

The microcontroller to be replaced formed the heart of a particular type of telephone, one that could prevent the dialling of unauthorised calls. This product was known as the Securacall, and consisted of a standard push-button telephone with extra circuitry to effect the required functions. It was intended that the replacement version would incorporate extra facilities. To demonstrate the enhanced version to interested parties, software was written in PASCAL, compiled into machine code, and downloaded to a Motorola 68000 general purpose development board, to simulate the functions of the new Securacall. This gave positive feedback, and allowed modification of the functions themselves, before the final specification was written. In choosing the new microcontroller chip the factors taken into account were: development time, ease of development, emulation capability, future modifications, and proven design path