Method and mechanism for maintaining integrity within SCSI bus with hot insertion
First Claim
1. A method of connecting a device to a single ended SCSI bus that is in use while maintaining data integrity, wherein said single ended SCSI bus includes a busy line and wherein said device includes a connector with signal pins that mate with said single ended SCSI bus, said method comprising the steps of:
- asserting a SCSI busy signal on said busy line a minimum time in advance of connecting said signal pins of said device to said single ended SCSI bus, said minimum time being the longest expected time before a SCSI communication will terminate;
starting a timing device adapted to provide an indication of when a predetermined time has elapsed;
coupling said signal pins of said device to said single ended SCSI bus;
testing said timing device; and
deasserting said SCSI busy signal when said predetermined time has elapsed.
0 Assignments
0 Petitions
Accused Products
Abstract
A mechanism and method for quiescing a SCSI bus by asserting the busy signal just prior to the SCSI signal pins making contact or decoupling during a hot modification. A hot modification is an insertion, removal or exchange of a device coupled to a SCSI interface bus while the system is operating (e.g., not powered down). By asserting the busy line for a predetermined and short period of time during the disturbance of the SCSI signal pins, glitches or noise introduced by the coupling or decoupling of the signal lines is isolated and prevented from causing transmission errors over the SCSI bus. According to the system described, any communication over the SCSI bus made just prior to the hot modification is allowed to complete before the signal pins are interrupted. For hot insertions, the system utilizes longer pins on the connector to assert the busy line just before coupling of the other pins of the connector. For removal, a special pair of short pins are placed on the connector to assert busy when decoupled. In either case, the busy line is then maintained as asserted for a predetermined period of time after the initial assertion to allow for communication over the SCSI bus to terminate before the hot modification.
-
Citations
9 Claims
-
1. A method of connecting a device to a single ended SCSI bus that is in use while maintaining data integrity, wherein said single ended SCSI bus includes a busy line and wherein said device includes a connector with signal pins that mate with said single ended SCSI bus, said method comprising the steps of:
-
asserting a SCSI busy signal on said busy line a minimum time in advance of connecting said signal pins of said device to said single ended SCSI bus, said minimum time being the longest expected time before a SCSI communication will terminate; starting a timing device adapted to provide an indication of when a predetermined time has elapsed; coupling said signal pins of said device to said single ended SCSI bus; testing said timing device; and deasserting said SCSI busy signal when said predetermined time has elapsed. - View Dependent Claims (2)
-
-
3. A system for connecting a device to a single ended SCSI bus that is in use while maintaining data integrity, wherein said single ended SCSI bus includes a busy line and wherein said device includes a connector with signal pins, said system comprising:
-
means connected to said single ended SCSI bus for asserting a SCSI busy signal on said busy line a minimum time in advance of connecting said signal pins of said device to said single ended SCSI bus, said minimum time being the longest expected time before a SCSI communication will terminate; means connected to said single ended SCSI bus for deasserting the SCSI busy signal a predetermined period after its assertion; and means for coupling said signal pins of said device to said single ended SCSI bus during the time that said busy signal is asserted. - View Dependent Claims (4, 5)
-
-
6. A system for coupling a device to a single ended SCSI bus that is in use while maintaining data integrity, wherein said single ended SCSI bus includes a busy line said system comprising:
-
a connector having a first side connected to said device and a second side connected to said single ended SCSI bus, said connector having a set of signal pins for carrying electrical signals, a set of long pins for making first contact when said first and second sides are connected, and a set of short pins for first breaking contact when said first and second sides are disconnected; and electrical circuitry connected to said connector and to said busy line for detecting said first contact through said long pins and said first breaking contact through said short pins and supplying a busy signal for a predetermined time on said busy line when first contact and said first breaking contact are detected. - View Dependent Claims (7)
-
-
8. A method of disconnecting a device from a single ended SCSI bus that is in use while maintaining data integrity, wherein said single ended SCSI bus includes a busy line and wherein said device includes a connector with signal pins that mate with said single ended SCSI bus, said method comprising the steps of:
-
asserting a SCSI busy signal on said busy line a minimum time in advance of disconnecting said signal pins of said device from said single ended SCSI bus, said minimum time being the longest expected time before a SCSI communication will terminate; starting a timing device adapted to provide an indication of when a predetermined time has elapsed; decoupling said signal pins of said device from said single ended SCSI bus; testing said timing device; and deasserting said SCSI busy signal when said predetermined time has elapsed. - View Dependent Claims (9)
-
Specification