Browse Prior Art Database

Use of a Shift Register to Replace Jumper Pins

IP.com Disclosure Number: IPCOM000036503D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Leininger, JC: AUTHOR

Abstract

This article describes a circuit arrangement which eliminates the need for jumper input/output (I/O) pins in very large-scale integration (VLSI) modules in a computer system by using a shift register to replace the jumper pins.

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Use of a Shift Register to Replace Jumper Pins

This article describes a circuit arrangement which eliminates the need for jumper input/output (I/O) pins in very large-scale integration (VLSI) modules in a computer system by using a shift register to replace the jumper pins.

VLSI designs often require a considerable number of jumper pins related to their physical environment (card plug position), use in the system, the amount of memory, etc. These pins are commonly controlled by setting their levels + or - with switches or plugging jumpers.

The circuit design disclosed herein eliminates the need for jumper I/O pins in VLSI modules. Usually jumpers or switches are set by removing a card from the system and they are not changed dynamically while system power is on. Except for systems with "hot plugability" the card must be removed, jumpers or switches set, the card reinserted and then the system powered up. Most systems have a "power-on reset" signal that is active during power-up and stays active for several milliseconds after power is good. This power-on reset is necessary for this circuit design to operate successfully.

The drawing shows the circuit design of this disclosure. In operation during power-up sequences, the "power-on reset" signal is active and clocks the jumper data into the external shift register. On the VLSI chip/module, a power-on count latch is set by the "power-on reset" signal and when this signal goes inactive, the power-on count latch causes a counter on the VLSI chip to count. While the counter is counting, the count latch causes shift clock signals to be sent to the external shift register and...