The Octave bits (Note <1:0>) are placed into two DMflag's before dividing N' by 4. Later they control the left-shifting of N" into lower octaves (the more shifts, the lower the octave). This scheme avoids using an M(transfer).

ADDITIONAL PROBLEMS

1. Design an advanced instrument to play 3-part harmony over a three octave range. Then extend to four parts and/or four octaves.

2. Design an instrument whose note frequencies are more accurate. A read-only memory may be used.

3. For these more complex instruments what code would be used to control the device? Is it necessary to transmit at a higher data rate? Can you encode each event (note or rest) into two characters?

4. Row would you modify the basic waveform generator to vary volume? - to change the shape of the waveform to better approximate a sine wave? - to approximate other (variable) musical instruments? - to change waveform under computer control?

5. It was assumed in the design above that when the same note is received two or more times in succession, no perceptible break would occur, and one continuous note would sound. Is this really so? If not, how would you redesign to make it so?

DESIGN OF INTERFACE TO A PAPER TAPE PUNCH

KEYWORDS: Paper tape punch, synchronization, nondigital behavior, transducer.

Several problems assume the existence of a T(paper tape punch); therefore we will design an interface for one. A unit of this type appears to be similar to the T(Teletype ASR 33; printer; keyboard; paper tape reader; punch). The design problem is given for several reasons; it is typical of the devices interfaced to digital systems, yet it is fairly simple; there are interesting pitfalls in the obvious synchronization technique, hence there will be extensions to the problem to increase the reliability; and the design will be carried out with both conventional and RTM logic. In any case, it is necessary to go outside the RTM logic framework for Transducer modules (e.g., to interface to the high current punching magnets).

PROBLEM STATEMENT

Design a system which will serve as an interface between the Teletype Model BRPE paper tape punch described below and the RTM system. The punch will appear as a conventional module in the RTM system.

DESIGN CONSIDERATIONS

The overall structure of a T(paper tape punch) as seen by an RTM user is shown in Figure PH-1. A register, the Punch Buffer, holds the eight bit character to be punched. The character is eventually punched on a one inch wide paper tape, and 10 characters are punched per linear inch of tape. The physical punch is manufactured by Teletype Corporation as the Model BRPE. The punch operates at the rate of 110 characters per second.

Figure PH-2 shows the internal structure of the T(paper tape punch) system of Figure PH-1 in the next stage of detail. In this figure the signals to the physical Teletype BRPE punch are depicted along with the logic that performs the actual punching process. In order to punch a character the Punch Buffer is

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