Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-07-20
2001-10-23
Beausoleil, Robert (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S108000, C710S108000
Reexamination Certificate
active
06308233
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a circuit allowing insertion and extraction of a board during normal operation, and more particularly to a circuit which detects a voltage of the board itself, opens/closes a buffer and regulates board reset timing when a board is inserted.
DESCRIPTION OF THE RELATED ART
In general, communication base station equipment and other complex electronic systems are formed with a system rack which receives a plurality of removable circuit boards. This configuration maximimizes flexibility and serviceability. When a fault occurs in a board of a communication system or an existing board needs to be replaced with a new board according to demand for a new service of communication system, the existing board currently residing in a card slot must be extracted. When a communication system requires a new board to meet the demand for the new service, the new board must be inserted into a card slot.
It is not difficult to insert a new board or to extract a failing board when a communication system is off. However, during normal operation of the communication system, insertion or extraction of a board can cause problems in the operation of the communication system by affecting the power source of the communication system and by initializing the inserted board in an unreliable manner. Currently, there are methods for inserting and extracting a board during normal operation of the communication system. Most conventional methods provide a ground connection to the card first and a power supply source to the card later. Even though this method can still render a communication system unstable, it is widely used because an additional circuit is not required to facilitate inserting and extracting of a board.
Another known method is to construct a special circuit for inserting/extracting a board. The stabilizing circuit is supplied with power not from a system itself, but from an external source. This circuit is controlled by the power supplied from the system and the power enables part of the circuit to be stable.
A third method is to gradually apply power by using a resistance and a capacitance to allow the load of the whole communication system to increase gradually, thus avoiding power transients.
While the above stated methods for inserting/extracting a board try to keep the system stable, it is almost impossible to insert/extract a board only using the internal power, not power supplied from the external source. Since the operation of insertion and extraction are different from each other, known methods may allow one of insertion and extraction to be performed normally, while the other operation remains unreliable. In addition, a circuit for inserting/extracting a board is affected according to changes of the temperature. Furthermore, an additional circuit must be provided so that power is supplied from the external source.
U.S. Pat. No., 5,247,619 discloses a method according to the prior art. This invention provides a method for performing insertion/extraction of a board in an on-line system. This method includes an auxiliary switch circuit which is utilized with software. According to this method, after an LED indicator indicates an ON condition, an extraction condition is prepared. This invention has the advantage of obtaining system stability during an extraction operation. On the other hand, it is complicated to utilize this method because handling of a switch must be made from an external controller. Consequently, it is not easy to perform insertion/extraction of a board into/from a system according to this method.
U.S. Pat. Nos., 5,384,492 and 5,272,584 disclose other methods according to the prior art for inserting/extracting a board in an on-line system. The invention in both patents is characterized by accelerating power to the board.
SUMMARY OF THE INVENTION
The present invention provides a circuit allowing insertion and extraction of a board in a system during normal operation by utilizing a stabilizing circuit which monitors gradually changing voltage, prohibits signal transfer between the system and the board during insertion/extraction and thereby enables normal operation of the system during an insertion/extraction operation.
One preferred embodiment of a circuit allowing insertion and extraction of a board in the system during normal operation includes a monitoring circuit which detects the voltage of the board itself, a bilateral buffer interposed in the signal lines between the board and the system and means to open or close the bilateral buffer according to the output of the monitoring circuit.
When the detected voltage of a board is over a predetermined level, a board reset timing circuit is preferably initialized to maintain the board in a reset state for a predetermined time after a sufficient voltage is present, thereby insuring a reliable reset condition. During the predetermined time, the buffer is disabled, thereby preventing signals from passing between the board and the system while the board is in the reset state.
Preferably, a circuit for detecting and monitoring the voltage of a board includes: a power supervisor integrated circuit (supervisor IC) to which Vcc of the board is applied via a SENSE terminal. The supervisor IC further includes: a CT terminal which is grounded via a capacitor with a capacitance C
T
, a REF terminal which is grounded via a capacitor with a predetermined value, and a RESET terminal is grounded via a resistance R
4
. A transistor is included to which one end of the resistance R
4
is connected to a base of the transistor via resistance R
3
, the output of the RESET terminal of the IC is inputted via resistance R
1
to an emitter of the transistor, a resistance R
2
is connected in parallel with the emitter and the base, and a collector is grounded via resistance R
5
. A system {overscore (RESET)} signal is outputted through the collector terminal.
Preferably, the capacitor C
t
(F) has a value given as C
t
(F)=t
d
(s)/1.3×104), where t
d
(s) is a board reset time. Preferably, the means to open or close a bilateral buffer is an inverter. It is also preferable that so as to variably regulate the board reset timing, the inverter inputs the system {overscore (RESET)} signal to the bilateral buffer, and the bilateral buffer receives the output signal of the inverter and Vcc is applied between the inverter and the bilateral buffer connected with the inverter. Until the detected voltage reaches a predetermined level, the output of the system {overscore (RESET)} signal is low. When the detected voltage exceeds the predetermined level, the voltage preferably initializes the reset timer. Upon expiration of the reset timer, the board enters a normal operating state and the bilateral buffer is enabled to pass signals.
In extracting the board from the system, if the detected voltage is less than the predetermined level, the bilateral buffer is disabled which prohibits signals from passing and makes the extraction of the board possible.
REFERENCES:
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patent: 4766601 (1988-08-01), Hammond
patent: 5092799 (1992-03-01), Kimura
patent: 5247619 (1993-09-01), Mutoh et al.
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patent: 5951660 (1999-09-01), Wonterghem
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Beausoleil Robert
Dilworth & Barrese LLP
Samsung Electronics Co,. Ltd.
Vo Tim
LandOfFree
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