Method and system for pipelining bus requests

In a system comprising a bus, a node coupled to said bus, and a bus coordinator coupled to said node for controlling access to said bus by said node, a method for transmitting information signals from said node onto said bus, comprising the steps of:

• sending an asserted bus request signal from said node to said bus coordinator;
• in response to said bus request signal, sending an asserted bus grant signal from said bus coordinator to said node to grant control of said bus to said node for a first tenure, said bus coordinator maintaining said grant signal in the asserted state as long as said bus request signal is asserted;
• transmitting information signals from said node onto said bus in response to said asserted grant signal;
• sending a deasserted bus request signal from said node to said bus coordinator prior to transmitting a last portion of said information signals;
• in response to said deasserted bus request signal, maintaining, by said bus coordinator, said bus grant signal in the asserted state for at least one extra clock cycle after said deasserted bus request signal is detected by said bus coordinator;
• during said extra clock cycle:
• transmitting said last portion of said information signals from said node onto said bus;
• sending a reasserted bus request signal from said node to said bus coordinator;
• further in response to said deasserted bus request signal, initiating, by said bus coordinator, an arbitration procedure to determine whether control of said bus is to be granted again to said node;
• and
• in response to a determination that control of said bus is to be granted again to said node, maintaining said bus grant signal in the asserted state to grant control of said bus to said node for a second tenure, said grant signal experiencing no change in state between said first and second tenures.

A bus system, comprising:

• a bus;
• a node coupled to said bus;
• and
• a bus coordinator coupled to said node for coordinating access to said bus by said node, said coordinator receiving an asserted bus request signal from said node and, in response, said coordinator sending an asserted bus grant signal to said node to grant control of said bus to said node for a first tenure, said coordinator maintaining said bus grant signal in the asserted state as long as said bus request signal is asserted, said coordinator further monitoring said bus request signal to detect any deassertion of said but request signal, and in response to a deassertion of said request signal, said bus coordinator maintaining said bus grant signal in the asserted state for at least one extra clock cycle after deassertion of said request signal is detected, said coordinator further, in response to a deassertion of said bus request signal, initiating an arbitration procedure to determine whether control of said bus is to be granted again to said node, and in response to a determination that control of said bus is to be granted again to said node, said bus coordinator maintaining said bus grant signal in the asserted state to grant control of said bus to said node for a second tenure, said grant signal experiencing no change in state between said first and second tenures.

A bus access coordinator for controlling access to a bus by a node, comprising:

• means for receiving an asserted bus request signal from the node;
• means for sending, in response to said bus request signal, an asserted bus grant signal to the node to grant control of the bus to the node for a first tenure, said sending means maintaining said grant signal in the asserted state as long as said bus request signal is asserted;
• means for monitoring said bus request signal to detect any deassertion of said bus request signal;
• means for maintaining, in response to a deassertion of said bus request signal, said bus grant signal in the asserted state for at least one extra clock cycle after deassertion of said request signal is detected;
• means for initiating, in response to a deassertion of said bus request signal, an arbitration procedure to determine whether control of said bus is to be granted again to said node;
• and
• means for maintaining, in response to a determination that control of said bus is to be granted again to said node, said bus grant signal in the asserted state to grant control of said bus to said node for a second tenure, said grant signal experiencing no change in state between said first and second tenures.