Distributed data bus sequencing for a system bus with separate address

Abstract

A data bus sequencer for use by nodes coupled to a system bus for associating data transactions and address transactions on the bus. The data bus sequencer includes means for tracking address and command transactions occurring on an address bus, the means for tracking producing a sequence number tag corresponding to each address and command transaction occurring on the address bus. Means for associating data transactions with address and command transactions stores the sequence number tags corresponding to address and command transactions for which data transactions are to be initiated by the node. Further included are means for tracking data transactions occurring on a data bus, means for comparing tracked data transactions to associated data transactions, and means for initiating data transactions on the data bus in response to the comparison. The data bus sequencer further includes means for driving the sequence tag for an address and command transaction to which a data transaction is associated on the data bus. Consistency check means includes means for tracking data transactions occurring on a data bus, and means for comparing tracked data transactions to sequence number tags driven on the data bus. The consistency check means indicates an error condition in response to the comparison if the sequence number tag most recently driven on the data bus is not equal to the counted number of data transactions which have occurred on the data bus.