Browse Prior Art Database

Programmable Instruction Cycle Time

IP.com Disclosure Number: IPCOM000050460D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Dixon, JD: AUTHOR [+2]

Abstract

A scheme is described that allows a microprocessor to match the data rate of an external device. When transferring data between a microprocessor and an external device, the data rate at which the device can send or receive the data can be considerably slower than the microprocessor speed. Depending on technology, the data may have to be presented to the device for several cycles, the device address may need to be extended, and the data strobe extended as well. This is usually accomplished by adding external latches on the signals to be extended and incurs added cost.

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Programmable Instruction Cycle Time

A scheme is described that allows a microprocessor to match the data rate of an external device. When transferring data between a microprocessor and an external device, the data rate at which the device can send or receive the data can be considerably slower than the microprocessor speed. Depending on technology, the data may have to be presented to the device for several cycles, the device address may need to be extended, and the data strobe extended as well. This is usually accomplished by adding external latches on the signals to be extended and incurs added cost.

A method is described here that extends the duration of the signal lines from the microprocessor to the device. The instruction or instructions which present the device address, data and strobe signals are redefined so that a field of 2 or more bits is identified as the number of cycles the instruction will take. For example, if 2 bits were identified, then the instruction could take from 1 to 4 cycles and if 3 bits were identified, then the instruction would take from 1 to 8 cycles, etc. This feature provides for a programmable "slow motion" effect so that the microprocessor can directly match the device speed by programming instead of using additional hardware.

Similarly, the instruction or instructions which present an address to the device and sample data into the microprocessor could also be defined with a 2 (or more)-bit field included so that the number of c...