Channel Tester With Microcode in Channel Processor for Repetitive Execution of Instruction for Testing Each Attached Device
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
A channel tester (also called an exerciser) is built into a channel processor and executes I/O instructions and responds to I/O interrupts and condition codes in a way that is normally done by a central processor. TIO (Test I/O) is a conventional test instruction executed by a central processor. The TIO instruction has the address of an I/O device, and during the execution of TIO the channel signals the addressed device and the device sends the channel a status byte. The channel then sends the central processor a condition code that is based on the status byte and tells whether the device is operational. The channel can also send the central processor a status word with additional information. A channel tester conventionally executes TIO for device address in order to detect an incorrect connection or other fault.