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Intercept Circuit for Connecting New Function Logic

IP.com Disclosure Number: IPCOM000046358D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Farrell, RH: AUTHOR [+3]

Abstract

An intercept circuit is described for adding a new function or feature to an existing I/O controller card design without having to release a new VLSI (very large-scale integration) module.

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Intercept Circuit for Connecting New Function Logic

An intercept circuit is described for adding a new function or feature to an existing I/O controller card design without having to release a new VLSI (very large-scale integration) module.

The circuit shown in the drawing allows the user to intercept control signals to and from a VLSI module l0 that interfaces with an I/O device 11 to enhance the function of the module 10 without the need to redesign same. The intercept circuit uses tri-state buffers 12 and 13 that are normally enabled by a voltage +V supplied by way of a pullup resistor 14. When the new function is not desired, the +V pull-up voltage enables the buffers 12 and 13 so that they may pass the appropriate signals to and from the VLSI module 10 and the remainder of the controller card logic 15.

When a new function is desired, a new function logic LSI module 16 is mounted on the controller card and is connected into the circuit, as shown. A ground connection in the new function logic module 16 is connected by way of conductor 17 to the pull-up resistor 14. This grounds the lower end of the pull-up resistor 14 and disables the tri- state buffers 12 and 13. The new function module 16 thereafter intercepts the control signals previously supplied to the buffers 12 and 13, modifies them to perform the desired new functions, and redrives them at the outputs of the now disabled tristate buffers 12 and 13.

The advantage of this intercept circuit is that a wor...