A communications bus for a digital device includes a credit-based flow control mechanism, in which a sending component maintains a local record of its credits. Credits are returned to the sender by pulsing a single-bit credit return line. A separate mechanism provides a count of available credits from the receiver, the separate mechanism not necessarily being current. The local record is compared to the count of credits from the separate mechanism over a pre-determined time interval, failure of the two values to agree at any time during the interval indicating a probable credit discrepancy. A credit discrepancy is confirmed, preferably by suspending certain bus activity for a sufficiently long period to account for any delay in propagating credit value changes, and re-comparing the values. Preferably, the bus communicates between internal components of an integrated circuit chip.