Thesis (Masters Diploma (Electrical Engineering) -- Cape Technikon, Cape Town,1991 / 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/1152 |
| Date | January 1991 |
| Creators | Keown, Harvey |
| Publisher | Cape Technikon |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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