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The control part of the system is comprised of a principal control loop and three subroutines. The control loop is a polling process which checks the DMflags, T-clock, and R-clock, for an indication that data is to be transmitted or received. On transmission, the data in the DMflag (T-data) is transferred to the DMflag (T-out), the data in the transmit buffer, T, is shifted left one bit, and the most significant bit (shifted to OVERFLOW) is placed in T-data prior to the next clock signal. On receiving input, each new bit is shifted into the receive buffer, R. When the start bit is shifted out of R into OVERFLOW, the nine bits of the message have been received. Thus, when OVERFLOW is set, the 5-bit channel number is transferred to the analog multiplexor switch which selects the appropriate channel, and an analog sample, is taken. The T(analog-to-digital) converts the analog sample to digital form and the data is transferred to the transmit buffer, T.

TELETROLA, A MUSICAL TERMINAL

Design by Michael Knudsen

KEYWORDS: Tone synthesis, frequency division, Teletype

Most of us are familiar with devices known as electronic music synthesizers. These usually consist of various analog tone generators driven by a human playing a keyboard. In this problem we shall deal with the design of a synthesizer which generates tones digitally, and is driven by incoming, serial digital data of the form used by a Teletype.

PROBLEM STATEMENT

Design a musical instrument which connects to a bit-serial communications line and interprets incoming characters as notes to be played. For the purposes of this problem, assume the bit serial line comes from a Teletype, hence the name Teletrola for the musical instrument. Since nearly all computers have interfaces for low-speed (10, 15 or 30 characters/sec) typewriter-like terminals and use bit-serial (or Teletype) format data, Teletrola could be easily interfaced with a computer.

The design should adhere to the following restrictions:

Technical Restrictions

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