Channel position signaling method and means

Abstract

Abstract POSITION INFORMATION ABOUT AN INTERRUPTED I/O DEVICE COMMUNICATED TO THE CPU AS A RESULT OF AN ERROR IN ITS CHANNEL, EVEN THROUGH NO ERROR OCCURRED IN THE I/O DEVICE. THE POSITIONAL INFORMATION ABOUT SHC I/O DEVICE IS CHOSEN IN RELATION TO THE EXECUTION STEPS IN A CHANNEL INSTRUCTION, SO THAT A RETRY MAY BE MADE OF THE CHANNEL INSTRUCTION BEING EXECUTED AT THE TIME OF THE CHANNEL ERROR. THE RECOVERY ACTION TO BE TAKEN AT THE I/O DEVICE FOR THE SAME CHANNEL INSTRUCTION VARIES WITH THE POSITIONAL INFORMATION EXISTING AT THE TIME OF THE CHANNEL ERROR. WITH START-STOP I/O DEVICES, THE INVENTION ENABLES A RETRY OF A SINGLE ERRONEOUSLY EXECUTED CHANNEL COMMAND BOTH DURING A COMMAND CHAINING OPERATION, AS WELL AS DURING NON-CHAINED COMMAND OPERATIONS. THE CHANNEL-I/O INTERFACE IS MONITORED BY A TIMEPOSITION SIGNALING CIRCUIT, WHICH DISCRETELY CYCLES AT DIFFERENT POINTS IN THE EXECUTION OF A CHANNEL INSTRUCTION (OR COMMAND) TO AN I/O DEVICE TO GENERATE CODES REPRESENTING RESPECTIVE TIME-POSITIONS DURING THE EXECUTION. AT THE MOMENT OF A CHANNEL ERROR, THE INPUT TO THE SIGNNALING CIRCUIT IS BLOCKED, SO THAT IT CONTINUES TO PROVIDE THE POSITION CODE EXISTING AT THE TIME OF THE CHANNEL ERROR. THE POSITION CODE IS TRANSMITTED INTO THE CHANNEL STATUS WORD OF A COMPUTER SYSTEM BY A CHANNEL INTERRUPT CAUSED BY THE CHANNEL ERROR. THEN, THE I/O MOVEMENT CONDITION EXISTING AT THE TIME OF THE ERROR IS OBTAINABLE FROM IN FORMATION IN THE CHANNEL STATUS WORD BY RELATING THE POSITION CODE TO THE PARTICULAR CHANNEL INSTRUCTION, SO THAT A RETRY OF THE CHANNEL INSTRUCTION CAN BE MADE.

Inventors

• 👤 William E Boehner
• 👤 Bruce L Mcgilvray

Bibliographic Details