Talking board interface - extends the microprocessor's vocabulary

2-52 - elektor february 1982 talking board interface The interface serves to transfer digital information from the talking board to the computer (RAM) memory. Since the talking board transmits bits at inter- vals of only 12.5 /is, they can"t possibly be transferred directly to RAM in the microprocessor. The interface, as shown in figure 1, consists of a buffer, in which the data can be temporarily stored, and several IC"s which look after the necess- ary timing of the various control signals. Only four wires are needed to connect the interface to the talking board by way of points D, U, I/O and of course, ground. The EXP wire link should be removed from the talking board. Five I/O lines must be available in the pp while the I/O timing (to control the address counters in the speech ROM"s) clocks a frame. As can be seen, data entering at the D input must be valid on the positive going edge of an I/O pulse. In addition, the figure shows that the actual data flow occurs during the f...