International Business Machines Corporation

Peter L Potvin

Gerald H Miracle

Quiedo J Carbone, Jr

Richard A Neuner

John R Flanagan

Daniel Francis Casper

Vahe A Minassian

A computer system employs a repeater unit which repowers a serial channel link. The repeater unit also monitors and records non-idle usage and errors for both directions of the repeated serial link. Non-idle usage of the serial link is recorded as a number of seconds that non-idle traffic flowed in the link over a given period of time. Link serial code violations and loss-of-light transitions are also counted. Link code violations are counted with an accuracy that permits targeted serial link bit-error rates, of no more than one bit error in approximately two months, to be accurately verified for the first time in a normal customer environment. The repeater unit permits an attached monitoring computer to read and reset all its usage and error counters as often as required by the customer, and without losing any counts of any counted event. The attached monitoring computer can also instruct the repeater unit to send certain diagnostic patterns or no-light and/or perform a remote wrap function to assist with link problem determinations.

Apparatus for repowering and monitoring serial links

A device control unit operating under the protocol of a parallel bus is connected by a serial link to a channel that is primarily adapted to operate under a different protocol with device control units connected by a serial link. An extender unit interconnects the parallel bus and the serial link and performs the specific operations of the parallel bus protocol. The channel and the extender unit send serial frames on the link for data transfer and associated operations. These frames are constructed according to a protocol that provides an intermediate step in translating between the protocol of the serial control units and the protocol of the parallel control units. The channel is operable in either mode (by microcode) and the new protocol permits the serial channel mode to be independent of the protocol of the parallel control unit and it permits the two modes to be closely similar in many features. New operations using the protocol reduce the delays that would otherwise be required in the communications between the channel and the extender unit. The serial link can be made longer when the delays are reduced.

Apparatus for communication between a device control unit having a

An asynchronous high-speed data interface for coupling a serial channel to a parallel control unit. A first state machine, running synchronously with the channel transmitter clock, controls the filling of a pair of dual-port input buffers in alternating fashion with frame contents bytes from incoming serial frames that have been deserialized and decoded. A second state machine, running synchronously with a second clock that is asynchronous with the channel transmitter clock, controls the transfer of the frame contents bytes from the selected input buffer to one of a pair of output buffers en route to the control unit. Upon detecting the receipt of the third incoming frame contents byte, the first state machine sets a start latch, causing the second state machine to begin transferring data from the selected input buffer to the selected output buffer while the input buffer is still being filled. Means are provided for disregarding the frame contents bytes that have been transferred to the selected output buffer if the frame is ultimately aborted.

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Holly Springs, NC, United States of America

Peter L Potvin