Development of an interfacing unit enabling a microcomputer to emulate IBM 3278

Abstract

IBM 3278 Display Station is used to display online information from the IBM mainframe system. It is controlled by IBM 3274 Control Unit through coaxial cable. At present the used of IBM mainframe has increased rapidly, and the components of IBM mainframe system expensive. Development was proposed to use inexpensive microcomputer as some of the IBM mainframe system’s components. This thesis was to develop an interface unit which will enable microcomputer to emulate IBM 3278. The transmission and protocol used in the coaxial cable must be studied, in order to develop an interface unit which will enable miocrocomputer to emulate IBM 3278. The protocol and transmission methods (between IBM 3278 and IBM 3274) found will explain some operating details of IBM 3278 and IBM 3274. It was found that the protocol used in coaxial cable between IBM 3274 and IBM 3278 is not Binary Synchronous Communication or other standard protocol. The protocol used was developed by IBM, and the details of this protocol are not available to public. Using the hardware developed, protocol was captured and tested. The hardware developed was found to be satisfactory, but it cannot be used to communicate directly with IBM 3274 Control Unit because the CPU speed is not fast enough. It was calculated that the CPU must responses to IBM 3274 polling within 5 microseconds. At present there are two CPU which are suitable for this application, 8X305 and 82C570. As a result of this study, future development into this field is possible, also it can lead to future development of emulating the following IBM mainframe system’s components, IBM 3278 and IBM 3279.