Browse Prior Art Database

I/O Processor Microcode Trace Facility

IP.com Disclosure Number: IPCOM000061585D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Hung, TC: AUTHOR [+5]

Abstract

An input/output processor (IOP) microcode trace facility uses a simulated spooler and existing host trace facility to provide an on-line trace facility while preserving the real-time environment (no breakpoints or instruction stepping which would suspend the operation of code). The trace facility collects trace data needed to understand the internal workings of the microcode in such a way as to simulate a spooler. It then utilizes an existent trace facility running on the host processor to present the data in a desirable format to the end user. As shown in Fig. 1, the IOP internal microcode trace facility relies on preset trace points (defined by the microcoder) which are compiled into the microcode.

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I/O Processor Microcode Trace Facility

An input/output processor (IOP) microcode trace facility uses a simulated spooler and existing host trace facility to provide an on-line trace facility while preserving the real-time environment (no breakpoints or instruction stepping which would suspend the operation of code). The trace facility collects trace data needed to understand the internal workings of the microcode in such a way as to simulate a spooler. It then utilizes an existent trace facility running on the host processor to present the data in a desirable format to the end user. As shown in Fig. 1, the IOP internal microcode trace facility relies on preset trace points (defined by the microcoder) which are compiled into the microcode. These trace points are always present in the code, and the trace data collection mechanism is controlled by start and stop trace commands issued to the IOP from the host system. When a trace point is hit in the executing microcode, the trace data is saved in an IOP buffer and the buffer is sent back to the system and placed in main store when it is full. Sending the trace buffer to the system whenever it is full, and using several trace buffers in a round- robin fashion, allows the trace to be run for an extended period of time, and is the basis for the simulated spooler. The host system saves the trace data and provides the mechanism to format and print the data collected by the IOP. In an IOP multitasking environment, a trace manager task is created to handle Start Trace and Stop Trace commands from the host processor. When a Start Trace command is received, an indicator in the IOP is set (and similarly reset on Stop Trace commands). The Trace Manager task also handles sending of IOP trace buffers to the host. Since trace points are embedded in the executing task's microcode, each time a trace point is hit, a Trace Point Handler (TPH) is called. The TPH determines via the Start Trace Indicator whether or not trace data is to be collected. If so, a Trace Data Collection (T...