Design and development of an interface board between a minicomputer and a CDC printer with a memory buffer and a programmable vertical format throw

Abstract

Brown Davis and McCorquodale is one of the major suppliers of cheques to the banking industry. To produce these cheques they use a number of different print systems, one of which comprises of a minicomputer, an industry standard tape deck and two printers, a Diablo daisywheel and a Control Data Corporation (CDC) printer which was extensively modified to cater for the requirements of the cheque printing industry. The CDC printer is used to print the code line on the cheques using magnetic ink. After each line is printed the computer sends a form feed command which causes the printer to throw paper. This throw is controlled by a paper tape, known as a Vertical Format Unit tape, or rather a VFU tape. This tape has holes punched into it at specific places which determine the amount of paper throw also known as vertical feed. The holes are sensed by brushes which are pulled up to 5 volt when they pass over a hole and touch a roller connected to the 5 volt line. This system, being of an electro-mechanical nature, is prone to faults and causes much down time due to mechanical wear on the brushes and dirt on the roller. This means that the brushes have to be adjusted and therefore also means that the timing has to be readjusted each time. The timing relationships are discussed in Section 2.B