Hardware Interface Developments for the D17B Computer
C. H. Beck
The hardware interfaces that have been developed by the Systems Laborator consiste of the I/O interfaces requried to connect the D17B to an electric typewriter and a paper tape reader/punch. Table 1 lists the D17B code for octal and control characters. The peripheral device surrently being used is a Friden Flexowriter. This device is commonly available as government excess ADP equipment. Figure 1 is a schematic of the interconnections between the Flexowriter and the D17B. Interface design requires electronic and functional considerations. Table 2 lists the Flexowriter code modifications.
Figure 2 is a block diagram of the electronic circuits required for conditioning the input signals to the D17B from the Flexowriter. These circuits are required for the purposes of suppressing noise, changing voltage levels, inverting the signals from positive to negative logic, shortening the pulses, delaying the timing pulse, and generating the complement. Figure 3 illustrates the effect of these circuits on the Flexowriter waveforms. Figure 4 illustrates the waveshaping accomplished fir the timing pulse. Figure 5 is a block diagram of the electronic circuits required for conditioning the input signals to the Flexowriter from the D17B. These circuits are required for stretching or storing the information pulses, delaying the timing pulse, changing voltage levels, and inverting the signals from negative to positive logic.
The Flexowriter provides for typewriter keyboard or paper tape entry of data or instructions into the D17B in octal format rather than binary. The capability of retaining a hard copy typed record or a punched paper tape corresponding to the program and data being loaded is very desirable.
Hard copy typed output and punched paper tape output are also available. A CRT display scope is available for output monitoring of any memory location.
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