Method and apparatus for controlled removal and insertion of circuit modules

An electrical circuit arrangement comprising:

• a plurality of connectors each for removably engaging a circuit module comprising circuits for generating control signals;
• a data transmission bus connected to said connectors for the transmission of data between said connectors;
• clock circuit means for providing bus access clock pulses to said connectors;
• control circuit means connected to each of said connectors and to said bus and including bus access circuit means for determining bus access entitlement, said control circuit means responsive to a predetermined control signal from a circuit module engaging any one of said connectors to inhibit said clock circuit means after gaining bus access entitlement, thereby preventing the transmission of data between said bus and any of said connectors for as long as said predetermined signal is present.

In an electrical circuit comprising a plurality of circuit modules, a bus for interconnecting said plurality of circuit modules, power supply means for supplying electrical power to said modules, and circuit means for controlling access to said bus, the method of powering down one of said circuit modules comprising the steps of:

• a. transmitting a control signal from said one module to said circuit means for controlling said circuit means;
• b. in response to said control signal, seizing said bus by said circuit means upon completion of a bus transaction by another of said plurality of circuit modules;
• c. controlling said bus to prevent the transmission of signals between said bus and any of said plurality of circuit modules;
• and;
• d. thereafter, disconnecting said one circuit module from said power supply means under control of said circuit means.

In an electrical circuit comprising a plurality of connectors connected to a data transmission bus, a plurality of circuit modules for insertion in said connectors, a control circuit, and clock circuitry for generating bus access clock pulses for controlling communications between said connectors and said bus, the method of controlling said electrical circuit during insertion and removal of said modules into and from said connectors comprising the steps of:

• a. generating a control signal to said control circuit prior to insertion and removal of a first selected one of said modules;
• b. in response to said control signal, first seizing control of said bus by said control circuit upon completion of a bus transaction by another of said plurality of circuit modules to prevent access to said bus by any of said modules, and secondly disabling said clock circuitry to prevent communications between said connectors and said bus;
• c. generating a second control signal to said control circuit upon completion of insertion or removal of said selected module;
• and
• d. relinquishing control of said bus by said control circuit and enabling said clock circuitry in response to said second control signal.

In a data processor having a plurality of removable circuit modules each having a plurality of conductors, a plurality of connectors for supporting said modules and each of said connectors comprising a plurality of conductors for engaging conductors of modules supported therein, a data transmission bus interconnecting said connectors, clock circuitry for providing bus access clock pulses controlling communications between said connectors and said bus, and power supply circuitry for supplying electrical power to said connectors, an arrangement for controlling operation of said bus during insertion and removal of circuit modules into and from said connectors, comprising:

• a control circuit;
• switch means on each of said modules;
• said switch means connectable to said power supply circuitry and to said control circuit via conductors on said modules and on said connectors and operable to a first state to activate a control signal and to a second state to deactivate said control signal;
• said control circuit being responsive to activation of said control signal supplied via one of said connectors to first inhibit said clock circuitry from providing said clock pulses to said connectors thereby inhibiting communication between said bus and any of said plurality of connectors, and to subsequently inhibit said power supply circuitry from supplying power to said one connector;
• said control signal being deactivated upon disengagement of conductors of a module from conductors of said one connector during module removal and upon operation of said switch means on a module in said one connector to said second state during module insertion;
• said switch means on said module in said one connector transmitting a power control signal to said power supply circuitry when operated to said second state;
• said power supply circuitry responsive to said power control signal to supply power to said one connector, and said control circuit being responsive to said deactivation of said control signal to generate an enable signal to enable said clock circuitry to provide said clock pulses to said connectors.

An electrical circuit comprising:

• a plurality of removable circuit boards;
• a plurality of connectors for pluggably engaging said boards;
• a system ground contact point connected to said connectors;
• a data transmission bus interconnecting said connectors;
• a clock circuit for providing bus access clock pulses to said connectors;
• power supply circuitry for supplying electrical power to each of said boards;
• a control circuit located remote from said removable circuit board;
• switch means on each of said boards connected to said power supply circuitry, said ground contact point, and said control circuit by means of said connectors and having a first state and a second state wherein said switch in said second state provides a closed path from said ground contact point to said control circuit;
• said control circuit being responsive to said switch means on one of said boards being operated from said first state to said second state to inhibit said clock circuit, thereby preventing the transmission of signals between said bus and any of said connectors and to subsequently inhibit said power supply circuitry from supplying power to said one board and said control circuit being further responsive to a breaking of said closed path through said switch caused by removal of said one board from a corresponding connector to generate a clock enable signal to said clock circuit.

A bus structure comprising:

• a plurality of connector means for receiving and retaining circuit modules;
• a transmission bus connected to said connector means for performing transmission operations between said connector means;
• clock circuit means for providing bus access clock pulses to each of said connectors;
• control circuit means connected to said connector means and said clock circuit means and responsive to a first control signal from one of said connector means indicating insertion or removal of a circuit module in said one connector means for inhibiting said clock circuit means from providing said bus access clock pulses to said plurality of connector means thereby preventing transmission of signals between any of said connector means and said transmission bus and responsive to a second control signal indicating completion of insertion or removal of a circuit module in said one connector means to enable said clock circuit means.