Data output impedance control
AssigneeInternational Business Machines Corporation
InventorsAlfred L. Sartwell, Endre P. Thoma
Life of this patent
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Abstract
The present invention provides an apparatus and method for monitoring the functioning of a special operational mode on an integrated circuit module without the need for a special or dedicated pin. By monitoring the data output pins of the module operation in a special operational mode and premature interruption thereof, is detected. Delayed transition from a state of low impedance to a state of high impedance during the data output cycle is indicative of the special operational mode. The modules which usually have tri-state devices on their output lines are provided with delay circuitry to delay the transition of the tri-state device, during the data output cycle, from a state of low impedance to a state of high impedance while the device remains in a special operating mode.
Claims8
An output control circuit for monitoring an operational mode of an integrated circuit module comprising:
- a tri-state device with an input connection for the reception of data, an output connection for the transmission of data, and a disable control responsive to a disable signal for changing the tri-state device from a state of low impedance which allows the transmission of data to a state of high impedance which prevents the transmission of data;
- disable means which produces a disable signal upon completion of said operational mode, means for switching the disable signal between a first line and a second line, said first and second lines being connected to the disable control of the tri-state device, and wherein the first line allows an immediate transmission of the disable signal to said disable control and the second line has delay means for delaying the transmission of the disable signal to the disable control;
- detection means for detecting the initiation of the operational mode and in response thereto setting the switching means to connect the disable signal to the second line;
- and
- monitoring means for monitoring the operation of the integrated circuit module and upon detection of a premature interruption of said operational mode setting the switching means to connect the disable signal to the first line.
An integrated circuit module having a plurality of output lines, each of said plurality of output lines having an output control circuit associated therewith, the output control circuit comprising:
- a tri-state device with an input connection for the reception of data, an output connection for the transmission of data, and a disable control responsive to a disable signal for changing the tri-state device from a state of low impedance which allows the transmission of data to a state of high impedance which prevents the transmission of data;
- disable means which produces a disable signal, means for switching the disable signal between a first line and a second line, said first and second lines being connected to the disable control of the tri-state device, and wherein the first line allows an instantaneous transmission of the disable signal to said disable control and the second line has delay means for delaying the transmission of the disable signal to the disable control;
- condition detection means for detecting the initiation of a condition and in response thereto setting the switching means to connect the disable signal to the second line;
- and
- monitoring means for monitoring the condition and upon detection of a change of said condition setting the switching means to connect the disable signal to the first line, whereby different conditions can be simultaneously monitored to control the output of respective output lines.
Dependencies are inferred from the claim text.