Browse Prior Art Database

Clock Transition, Self-Timed, Off-Chip Driver

IP.com Disclosure Number: IPCOM000035300D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Nguyen, QQ: AUTHOR

Abstract

An off-chip driver (OCD) is triggered by detecting a clock transition following a set pulse and fires on every clock transition thereafter so long as data is continuously fed from input shift registers.

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Clock Transition, Self-Timed, Off-Chip Driver

An off-chip driver (OCD) is triggered by detecting a clock transition following a set pulse and fires on every clock transition thereafter so long as data is continuously fed from input shift registers.

Referring to the figure, devices T1 through T12 form a self-timed, boosted driver. Devices T20 through T38 are used to detect a clock transition and to tri- state the driver. An input signal from shift registers 2 and 4 is fed to the gate of transistor T12 at node N1 and is continuously presented at node N1 regardless of whether the OCD is activated or not (still in HiZ state). Clock SCLK selects one of two bits of data from two parallel rows of shift registers 2 and 4 and inputs resultant data to the OCD at node N1. Devices T8, T20, and T30 are used for punch-through protection and have no other effect on operation of the circuit.

The OCD is reset into HiZ state by having signal SOE in high state. Nodes N8 and N11, which are pre-charged high by signal SOE through devices T24 and T34, pull nodes N4 and N2 to ground through transistors T20, T21, and T22 and T30, T31, and T32, respectively. Gates of transistors T6 and T10 are connected to the complement of SOE, CSOE to save power and ensure that nodes N4 and N2 are completely pulled to ground. An input signal at node N1 has no effect on output SIO.

To activate the OCD from the HiZ state, signal SOE must be driven from high to low state first and clock SCLK has to make a transition in either direction. As signal SOE goes from high to low, the OCD is still in HiZ state until SCLK makes a transition. Thus, the OCD does not depend on the state of clock SCLK, but on a clock transition. Two sets of clock transition detectors, circuit portions 6 and 8 are used to tri-state the...