Browse Prior Art Database

Data Flow Clock

IP.com Disclosure Number: IPCOM000076213D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Duvalsaint, JJ: AUTHOR [+2]

Abstract

In synchronously multiplexing between computing systems having different data rates on a cycle-steal basis, the transmission frequency is normally controlled by synchronizing lines timed external to the computer. This requires either computer programming loops or extensive timing control hardware external to the computer. This data flow clock provides easy programming control for setting transmission frequency over a broad range.

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Data Flow Clock

In synchronously multiplexing between computing systems having different data rates on a cycle-steal basis, the transmission frequency is normally controlled by synchronizing lines timed external to the computer. This requires either computer programming loops or extensive timing control hardware external to the computer. This data flow clock provides easy programming control for setting transmission frequency over a broad range.

The clock includes variable-frequency oscillator 1 having a digitally programmable frequency provided by range-bit decoders 2, 3, 4. Oscillator 1 drives presettable counter 5. The control for the transmission frequency provided on line 6 is determined by programming the word-cycle period as a combination of oscillator frequency and cycle counts.

Data in bus 7 provides the two's complement of the data word for loading into counter 5. The range bits are provided to decoders 2, 3, 4 to provide the proper range to oscillator 1, which operates as a single-shot under control of a loading pulse at 9. Data out is provided to output buffers on bus 8. Oscillator 1 also receives a synchronizing start pulse at 10 to initiate the counting operation of the clock. The synchronizing pulse is also provided to zero decoder 11 which interrogates the output of counter 5 to determine if it is zero.

Since a timing count was loaded into counter 5, decoder 11 does not detect a zero. The chosen range single-shot is activated through line 12 and t...