Intelligent point of sale terminal thesis

Abstract

The main reason for this project was "import replacement", as all our existing Point of Sale and Electronic Equipment had to be imported from Japan. After the Government I s steps to curb imports by placing extremely high levies on imported goods, it was decided to produce a completely local product. From past experience it was obvious that customer requirements varied greatly. This gave rise to the inception of a modular system, enabling the customer to "mix and match" modules to their requirements. The"concept is to use a HOST computer controlling a differential communications line with a maximum of 255 terminals which are all individually addressable. Each individual terminal would in turn control an internal differential communications line, called PNET, which is an acronym for "Peripheral Network". A decision was made to make all the peripherals intelligent, thereby alleviating the processor of all menial tasks. All peripherals local to the terminal would be connected to this network. The configuration can be seen graphically by refering to Figure 0-1. The communications protocol used is more sophisticated than that used for RS232 devices. The protocol has a POLL - ACKNOWLEDGE structure, where the HOST has complete control of the loop.