Browse Prior Art Database

High Performance Tri-State Select Switch

IP.com Disclosure Number: IPCOM000049001D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Knepper, LE: AUTHOR

Abstract

The disclosed circuit receives input logic signal levels of 0.6 V and 2.4 V and provides true and complement signals of 0.3 V and 1.7 V for selecting and deselecting banks of tri-state drivers (not shown) of the type requiring base drive for the inhibit inputs. The bank of drivers (not shown) driving to the "left" is controlled by line "DSL", and conversely the bank of drivers (not shown) driving to the "right" is controlled by "DSR". Thus, using the disclosed circuit, tri-state drivers can be configured as a 1-byte bidirectional buffer.

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High Performance Tri-State Select Switch

The disclosed circuit receives input logic signal levels of 0.6 V and 2.4 V and provides true and complement signals of 0.3 V and 1.7 V for selecting and deselecting banks of tri-state drivers (not shown) of the type requiring base drive for the inhibit inputs. The bank of drivers (not shown) driving to the "left" is controlled by line "DSL", and conversely the bank of drivers (not shown) driving to the "right" is controlled by "DSR". Thus, using the disclosed circuit, tri-state drivers can be configured as a 1-byte bidirectional buffer.

The circuit operates as follows: Assume the inhibit (I) input is down (0.6 V). Transistor T6 is on, holding T7, T8, T12 and T13 OFF. If the direction (D) input is low (0.6 V), T3 is on, holding T4 OFF. Since T4 and T5 form a current switch, T5 is ON. Thus, Tl pulls "DSL" UP and turns ON T11, which aids in pulling "DSR" DOWN. At the same time T2 is pulled DOWN, which allows T10 to turn OFF. With "DSL" high (1.7 V) and "DSR" low (0.3 V), the drivers driving "left" are deselected (disabled) and the drivers driving "right" are selected (enabled).

Again, assume "I" is DOWN. If "D" is high (2.4 V), T3 is OFF, T4 turns ON, and T5 turns OFF, so T2 pulls "DSR" UP while turning T10 ON which pulls "DSL" DOWN. Simultaneously, T1 is pulled DOWN, turning T11 OFF. In this state. the drivers driving "left" are selected and those driving "right" are deselected.

When "I" is high (2.4 V), T6 turns OFF and T7...