British Telecommunications Engineering 

Volume 6 Part 4 page 284

Intelligent Serial Input/Output Module for STEbus

An intelligent serial input/output (I/O) card — the first for the STEbus — is now available from British Telecom Microprocessor Systems. Offering four fully-buffered serial channels, the 4500 features an on-board processor which minimises bus I/O by processing data locally, freeing up the STEbus and optimising system bandwidth. High-performance arithmetic and real-time clock functions can be included on-card, and provide significant enhancement capabilities for STEbus systems.

The provision of local intelligence by an on-board Z80A CPU provides systems designers with the means to process serial data prior to accessing the system’s internal STEbus. Such a distributed processing scheme relieves the STEbus master CPU from significant processing overheads, so that overall system performance and bus bandwidth are optimised. For example, incoming data from up to four sensors can be concentrated and analysed before transmitting a status report to the master; or outgoing data could be sent to a number of seperate VDUs and printers with data protocol conversion being handled locally.

All four I/O channels are driven by two Zilog Z8531 SCCs, and offer flexible asynchronous RS232 communications facilities. This capability is backed by an extensive 48K RAM buffer. Each channel is brought to the front edge of the card on a 10-way shrouded header; when connected via ribbon cable to a 9-pin male D-type connector, this offers compatibility with the serial port of an IBM AT or compatible computer.

The 4500 also offers powerful enhancement features for any STEbus system. A socket for AMD’s Am9511A arithmetic processor allows the board to handle complex fixed- or floating-point mathematical operations, including full trigonometric functions. This chip is designed specifically for 8 bit I/O systems, but employs internal 16/32 bit architecture for maximum precision, to allow the computational capability of an STEbus system to be extended in a cost-effective manner. Another socket for a real-time clock extends the applications potential of the 4500 to timing/dating communications, and/or implementing programmable-alarm/stopwatch facilities. This facility is battery-backed for up to 10 years.

Forming part of BT’s Martello range of STEbus systems building blocks, the 4500 comes with a monitor in ROM, and epitomises the thought behind this series of systems products: by distributing intelligence throughout the STEbus and relieving the master CPU of many tasks, true parallel processing can now be achieved, so that technically-efficient solutions can be realised in the minimum of time.

4500 intelligent serial I/O card for STEbus