Gary Lee Stevens

US Patent:

51192926, Jun 2, 1992

Filed:

Jul 21, 1989

Appl. No.:

7/384824

Inventors:

Lauren D. Baker - Westford MA
Gary W. Stevens - Whitinsville MA
William C. Herbst - Franklin MA

Assignee:

Clearpoint Research Corporation - Hopkinton MA

International Classification:

G06F 1336

US Classification:

395725

Abstract:

A first-type bus device is designed for use in a computer system having one or more second-type bus devices. The second-type devices practice a round robin arbitration scheme, but the first type devices do not. According to the round-robin scheme, a second-type device which wins an arbitration asserts its ID on the system bus, each second-type device seeking to arbitrate compares its ID with that asserted by the current bus master, and uses that comparison to determine whether to assert its ID during arbitration in a high or low priority manner. The first-type bus device includes means for assuring that first-type and second-type devices never arbitrate at the same time. During arbitration, first-type devices only assert their ID number in one priority. Unlike second-type devices, they cannot assert their ID either in a high or low priority manner. Each first-type device has means for being given a selectable ID number, but when a first type device becomes bus master, it asserts an ID number which is independent of its selectable ID number.

US Patent:

51014793, Mar 31, 1992

Filed:

Jul 21, 1989

Appl. No.:

7/384246

Inventors:

Lauren D. Baker - Westford MA
Gary W. Stevens - Whitinsville MA
William C. Herbst - Franklin MA

Assignee:

Clearpoint Research Corporation - Hopkinton MA

International Classification:

G06F 304
G06F 1300

US Classification:

395325

Abstract:

A bus device of a first type is designed to work with a bus devices of a second type. A bus device of the second type, when it is a slave in a bus transaction, issues an ACK if it can respond to the command on time, a NO ACK if it can't respond at all, a STALL if it expects to be able to respond with only a short delay, and a RETRY if it expects to be able to respond, but only after a long delay. Slave Bus devices of the second type also monitor the length of time that they assert the STALL signal, and if they assert if for more than a predetermined period, they replace the STALL signal with a RETRY. Bus devices of the second type, when they are master in a bus transaction, respond to a NO ACK by terminating a transaction in one way and to a RETRY by terminating the transaction in a different way. The bus devices of the first type provided by the present invention, although they are designed for use in conjunction with the second type bus devices, have no means for replacing a STALL with a RETRY when they are slaves in a bus transaction, and no means for responding to a NO ACK and a RETRY by terminating a transaction in a different manner when they are masters in a bus transaction.