Using an independent clock to coordinate access to registers by a peripheral device and a host system

A method for coordinating access to at least one data register between a computer network peripheral device and a host system, the at least one data register storing statistical data within a statistics module having an independent clock, said statistical data being related to transmission and reception of data packets by said host system via said network of computers, the method including the steps of:

• A. asserting a first valid signal from the computer network peripheral device, when a taken signal from said statistics module is not asserted, to indicate that the computer network peripheral device has new statistical data for updating said at least one data register within said statistics module, said first valid signal being synchronized to a peripheral device clock within said computer network peripheral device;
• B. asserting a second valid signal synchronized to said independent clock at the statistics module from the first valid signal being asserted in said step A;
• C. accepting said new statistical data by said statistics module from said computer network peripheral device when said second valid signal has been asserted in said step B;
• D. asserting said taken signal at said statistics module after said new statistical data has been substantially received by said statistics module from said computer network peripheral device, said taken signal being synchronized to said independent clock within said statistics module;
• E. deasserting said first valid signal synchronized to said peripheral device clock at said computer network peripheral device after said taken signal is asserted in said step D, to indicate that said computer network peripheral device is free to return to a foreground task;
• F. updating said at least one data register within said statistics module with said new statistical data while said taken signal at said statistics module is asserted;
• G. deasserting said taken signal at said statistics module after said at least one data register within said statistics module has been substantially updated;
• H. waiting to assert said first valid signal from the computer network peripheral device, when said taken signal from said statistics module is already asserted, until said taken signal is deasserted;
• I. asserting a first bus request signal from the host system on a bus interface to indicate that the host system is ready to read statistical data from said at least one data register, said first bus request signal being synchronized to a bus clock;
• J. asserting a second bus request signal synchronized to said independent clock at the statistics module from said first bus request signal being asserted;
• K. asserting a bus grant signal from said statistics module after said second bus request signal is asserted to indicate that the host system may read said statistical data from said at least one data register when said second valid signal is not asserted;
• L. reading said statistical data from said at least one data register by said host system via said bus interface after said bus grant signal has been asserted and if said second valid signal is not asserted;
• M. asserting a first bus preempt signal at the statistics module when the bus grant signal is asserted and the second valid signal is asserted, said first bus preempt signal being synchronized to said independent clock within said statistics module;
• N. asserting a second bus preempt signal synchronized to the bus clock at the bus interface from said first bus preempt signal being asserted to indicate to said host system that said at least one data register is to be updated;
• O. asserting a first preempt acknowledgment signal synchronized to the bus clock at the bus interface to indicate from the host system to the statistics module that said host system acknowledges that said at least one data register is to be updated;
• P. asserting a second preempt acknowledgment signal, synchronized to the independent clock at the statistics module from said first preempt acknowledgment signal being asserted, to indicate that said statistics module may update said at least one data register;
• and
• Q. performing said steps C-E after said second preempt acknowledgment signal has been asserted at said statistics module.

Apparatus for coordinating access to at least one data register between a peripheral device and a host system, the at least one data register being within a statistics module, the apparatus comprising:

• a peripheral device clock within said peripheral device for synchronizing operations within said peripheral device;
• an independent clock within said statistics module for synchronizing operations within said statistics module;
• a bus clock within a bus interface that couples said host system to said statistics module, said bus clock being within said bus interface for synchronizing operations within said bus interface;
• means for asserting a first valid signal from the peripheral device, when a taken signal from said statistics module is not asserted, to indicate that the peripheral device has new statistical data for updating said at least one data register within said statistics module, said first valid signal being synchronized to said peripheral device clock within said peripheral device;
• means for asserting a second valid signal synchronized to said independent clock at the statistics module from said first valid signal being asserted in said step A;
• means for accepting said new statistical data by said statistics module from said peripheral device when said second valid signal has been asserted in said step B;
• means for asserting said taken signal at said statistics module after said new statistical data has been substantially received by said statistics module from said peripheral device, said taken signal being synchronized to said independent clock within said statistic module;
• and
• means for deasserting said first valid signal synchronized to said peripheral device clock at said peripheral device after said taken signal is asserted in said step D, to indicate that said peripheral device is free to return to a foreground task.