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Bus Arbiter With Synchronized Reset

IP.com Disclosure Number: IPCOM000120655D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 89K

Publishing Venue

IBM

Related People

Fukuda, M: AUTHOR [+4]

Abstract

This article describes a new bus arbitration mechanism, Bus Arbiter with Synchronized Reset (BASR), which realizes a hot-pluggable multi- bus-master system. The BASR allows the system to keep running even when users add or remove a bus master. This characteristic is indispensable for fault-tolerant computers. Conventional fault-tolerant computers have two or more CPUs and I/Os running in parallel to improve Mean Time Between Failure (MTBF). For example, even if CPU-A in Fig. 1 has a problem and stops its operation, CPU-B continues the operation not to shutdown the system.

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

Bus Arbiter With Synchronized Reset

      This article describes a new bus arbitration mechanism,
Bus Arbiter with Synchronized Reset (BASR), which realizes a
hot-pluggable multi- bus-master system.  The BASR allows the system
to keep running even when users add or remove a bus master.  This
characteristic is indispensable for fault-tolerant computers.
Conventional fault-tolerant computers have two or more CPUs and I/Os
running in parallel to improve Mean Time Between Failure (MTBF).  For
example, even if CPU-A in Fig. 1 has a problem and stops its
operation, CPU-B continues the operation not to shutdown the system.

      A multi-bus-master system (see, e.g., Fig. 2) has two or more
bus masters that may try to use the shared bus at the same time.  To
avoid the access conflict on the bus, a bus arbiter is implemented on
the bus master.  Each bus master is assigned a unique priority code.
There are two basic methods: a fixed and variable priority control
method. The fixed priority control method gives a fixed priority code
to the bus masters.  It is simple, but it has a potential demerit
because the bus master that has higher bus priority may continue to
use the bus so that the other bus masters that have lower bus
priority cannot use the bus for a long time. On the contrary, the
variable priority control method changes the priorities with the bus
transaction to guarantee the fairness of bus usage.  Fig. 2 shows an
example of priority changing.  It should be noted that each bus
master must have a different priority.  If two or m...