1. Reference to Appendix
Appendix A is a part of the present disclosure, and is incorporated herein by reference in its entirety.
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
2. Field of the Invention
The present invention is related generally to monitoring operation of an integrated circuit and in particular to an integrated circuit output port for transporting information concerning any user selected operation of the integrated circuit from the integrated circuit.
3. Description of Related Art
As the form factor of hard disk drives become smaller and as the level integration for all disk drives becomes greater, the number of functions performed by a single integrated circuit in a disk drive increases substantially. As the number of functions performed by an integrated circuit increases, i.e., as the integration level increases, many of the functions are performed completely internally to the integrated circuit.
For functions that are performed completely internally, neither input, output, nor intermediate signals are available at pins of the integrated circuit. Further, the integrated circuit package size limits the number of available pins. The limited number of pins makes it unfeasible to route representative signals for each of the internal functions to a pin. Consequently, monitoring and testing of highly integrated circuits becomes problematic.
In the area of disk drive controllers, integration is becoming increasingly greater. Disk drive controller circuits that previously occupied a plug-in board are now packaged in a single integrated circuit. The plug-in boards had space for test points, switches for generating test signals, and other commonly known features that permitted relatively easy verification of the operation of the disk controller. When the same functionality is provided in an integrated circuit, there is no space for test points, switches and similar circuitry.
Therefore, typically, computer simulations are used to verify the operation of circuitry that is totally internal to an integrated circuit. Unfortunately, such simulations do not provide reliable information on the actual application performance of the integrated circuit. To obtain reliable application performance data, a way is needed to obtain information concerning all of the circuits within the integrated circuit while the circuits are in operation.