Browse Prior Art Database

Common On-Chip Processor Switch for Multiprocessor System

IP.com Disclosure Number: IPCOM000112333D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Brooks, JS: AUTHOR [+3]

Abstract

This article describes a method for selectively communicating with processors in a multiprocessor system via a Common On-Chip Processor (COP) interface, given that each processor has an identical fixed COP address.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Common On-Chip Processor Switch for Multiprocessor System

      This article describes a method for selectively communicating
with processors in a multiprocessor system via a Common On-Chip
Processor (COP) interface, given that each processor has an identical
fixed COP address.

      The COP is a control processor integrated into a chip.  The COP
allows a scan interface tool, such as the Engineering Support
Processor (ESP), to communicate with the chip.  ESP serially scans
the processor chip under test, allowing the user to set breakpoints,
single step, start, and stop the processor, or read and write the
processor's registers.

      A processor with a fixed COP address provides the required
addressability in a uniprocessor system, since all COP commands
directed to a processor are intended for the sole processor in the
system.  In fact, if the processor is the only device present on the
COP Bus, an address is not even necessary.  However, in a
multiprocessor system, a processor with a fixed COP address presents
a problem.  In this case, since each processor on the COP Bus has an
identical fixed address, it is not possible to selectively
communicate with a specific processor, or group of processors.  Each
processor will execute the same COP commands, making it impossible,
for example, to alter registers in one processor without altering the
same registers in all of the processors in the system.  Thus, a
multiprocessor system would look like a uniprocessor system to ESP.

      The Common On-Chip Processor Switch (COP Switch) is a device
attached to the COP Bus of a multiprocessor system and provides ESP,
or any scan interface tool, complete control in selecting which
processor or processor group is enabled to receive COP commands.
Communication with the COP Switch is established over the COP Bus,...