Self-contained high speed repeater/lun converter which controls all SCSI operations between the host SCSI bus and local SCSI bus

• US 5,925,120 A
• Filed: 06/18/1996
• Issued: 07/20/1999
• Est. Priority Date: 06/18/1996
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: McCarthy, James, Ballard, Curtis C., Arp, Ronald
• Primary Examiner(s): Sheikh, Ayaz R.
• Assistant Examiner(s): PHAN, RAYMOND NGAN
• Application Number:
  US08/666,796
• Time in Patent Office: 1,127 Days
• Field of Search: 395/308, 395/306, 395/309, 395/281, 395/438, 395/439, 395/822, 395/851, 395/858, 395/728, 395/311, 395/312, 395/284, 395/290, 395/292
• US Class Current: 710/314
• CPC Class Codes: G06F 13/4045 where the bus bridge performs an extender function

Abstract

A system and method is provided in a self-contained high speed repeater/LUN converter that allows for up to fifty-six devices to be connected to a narrow host SCSI bus via a local SCSI bus, where there does not have to be any modification of the devices on the local SCSI bus in terms of the SCSI interface. The host side of the converter supports either a single-ended or a differential SCSI bus. The converter controls all SCSI operations between the host SCSI bus and the local SCSI bus by means of a Corona device and a controller, where Corona controls all of the physical SCSI signals and the controller provides the capability to detect and respond to SCSI error conditions. The controller also selects the operation mode (LUN or repeater), board addresses, host bus type (single-ended or differential) selection, LUN/SCSI address mapping, and data mode (asynchronous, synchronous or fast synchronous) conversion.

Claims

1. A system for allowing more than eight devices to be effectively connected to a single narrow host SCSI bus, the system adapted to enable communications to occur between a host device having a first SCSI port, and a plurality of target devices, each having a SCSI port, the system comprising:

a host SCSI bus connected to the first SCSI port of the host device, the host device having a first host bus SCSI ID number used to identify the host device on said host SCSI bus;

a local SCSI bus connected to the SCSI ports of the plurality of target devices;

Corona means having a second SCSI port and a third SCSI port, for transferring the communications between the host device and one of the plurality of target devices selected by the host device, said Corona means connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, said Corona means having a second host bus SCSI ID number used to identify said Corona means on said host SCSI bus and a first local SCSI ID number used to identify said Corona means on said local SCSI bus, and for converting a SCSI logical unit number received from the host device to a second local bus SCSI ID number, said second local bus SCSI ID number identifying said selected target device on said local SCSI bus to establish communications between the host device and said selected target device, wherein said Corona means further comprises data path logic, connected between said controller and said host SCSI bus and said local SCSI bus, for converting communications between said host SCSI bus and said local SCSI bus into appropriate data mode; and

a controller connected to said Corona means for supporting and controlling said Corona means during SCSI operations between said host SCSI bus and said local SCSI bus.

2. The system according to claim 1, wherein said Corona means further comprises:

arbitration logic connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port for handling SCSI arbitration operations between said host SCSI bus and said local SCSI bus.

3. The system according to claim 1, wherein said data path logic further comprises:

a request state machine for transferring data from a local SCSI device to said host SCSI device and for generating a proper form of REQ on said host SCSI bus;

an acknowledge state machine for the transfer of data from said host SCSI device to said local SCSI device and for generating a proper form of ACK on said local SCSI bus; and

data path control logic for coordinating and controlling both the request and acknowledge state machines for proper data transfers.

4. The system according to claim 2, wherein said arbitration logic further comprises:

an arbitration state machine for controlling busy and select signals on the host SCSI bus and the local SCSI bus.

5. The system according to claim 2, wherein said arbitration logic further comprises:

a data line transfer logic for transferring data lines between the host SCSI bus and the local SCSI bus.

6. The system according to claim 2, wherein said arbitration logic further comprises:

an arbitration state machine for controlling the busy and select signals on the host SCSI bus and the local SCSI bus; and

a data line transfer logic for transferring data lines between the host SCSI bus and the local SCSI bus.

8. The system according to claim 1, wherein said second SCSI port of said Corona means has host single-ended and differential SCSI ports to enable said Corona means to be connected to and support either a single-ended or a differential host SCSI bus.

10. The system according to claim 1, wherein said controller performs LUN mapping between said host SCSI bus and said local SCSI bus.

12. The system according to claim 1, wherein said system is capable of operating in either LUN or repeater mode.

13. The system according to claim 12, wherein said controller controls whether the operation mode of said system is LUN or repeater.

7. A system for allowing more than eight devices to be effectively connected to a single narrow host SCSI bus, the system adapted to enable communications to occur between a host device having a first SCSI port, and a plurality of target devices, each having a SCSI port, the system comprising:

a host SCSI bus connected to the first SCSI port of the host device, the host device having a first host bus SCSI ID number used to identify the host device on said host SCSI bus;

a local SCSI bus connected to the SCSI ports of the plurality of target devices;

Corona means having a second SCSI port and a third SCSI port, for transferring the communications between the host device and one of the plurality of target devices selected by the host device, said Corona means connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, said Corona means having a second host bus SCSI ID number used to identify said Corona means on said host SCSI bus and a first local SCSI ID number used to identify said Corona means on said local SCSI bus, and for converting a SCSI logical unit number received from the host device to a second local bus SCSI ID number, said second local bus SCSI ID number identifying said selected target device on said local SCSI bus to establish communications between the host device and said selected target device, wherein said Corona means further comprises arbitration logic, connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, for handling arbitration operations between said host SCSI bus and said local SCSI bus, and data path logic, connected between said controller and said host SCSI bus and said local SCSI bus, for converting communications between said host SCSI bus and said local SCSI bus into the appropriate data mode; and

a controller connected to said Corona means for supporting and controlling said Corona means during SCSI operations between said host SCSI bus and said local SCSI bus.

9. A system for allowing more than eight devices to be effectively connected to a single narrow host SCSI bus, the system adapted to enable communications to occur between a host device having a first SCSI port, and a plurality of target devices, each having a SCSI port, the system comprising:

a host SCSI bus connected to the first SCSI port of the host device, the host device having a first host bus SCSI ID number used to identify the host device on said host SCSI bus;

a local SCSI bus connected to the SCSI ports of the plurality of target devices;

Corona means having a second SCSI port and a third SCSI port, for transferring the communications between the host device and one of the plurality of target devices selected by the host device, said Corona means connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, said Corona means having a second host bus SCSI ID number used to identify said Corona means on said host SCSI bus and a first local SCSI ID number used to identify said Corona means on said local SCSI bus, and for converting a SCSI logical unit number received from the host device to a second local bus SCSI ID number, said second local bus SCSI ID number identifying said selected target device on said local SCSI bus to establish communications between the host device and said selected target device, wherein said second SCSI port of said Corona means has host single-ended and differential SCSI ports to enable said Corona means to be connected to and support either a single-ended or a differential host SCSI bus; and

a controller connected to said Corona means for supporting and controlling said Corona means during SCSI operations between said host SCSI bus and said local SCSI bus, wherein said controller controls host SCSI bus type selection by said Corona means.

11. A system for allowing more than eight devices to be effectively connected to a single narrow host SCSI bus, the system adapted to enable communications to occur between a host device having a first SCSI port, and a plurality of target devices, each having a SCSI port, the system comprising:

a host SCSI bus connected to the first SCSI port of the host device, the host device having a first host bus SCSI ID number used to identify the host device on said host SCSI bus;

a local SCSI bus connected to the SCSI ports of the plurality of target devices;

Corona means having a second SCSI port and a third SCSI port, for transferring the communications between the host device and one of the plurality of target devices selected by the host device, said Corona means connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, said Corona means having a second host bus SCSI ID number used to identify said Corona means on said host SCSI bus and a first local SCSI ID number used to identify said Corona means on said local SCSI bus, and for converting a SCSI logical unit number received from the host device to a second local bus SCSI ID number, said second local bus SCSI ID number identifying said selected target device on said local SCSI bus to establish communications between the host device and said selected target device; and

a controller connected to said Corona means for supporting and controlling said Corona means during SCSI operations between said host SCSI bus and said local SCSI bus, wherein said controller detects and responds to SCSI error conditions on either said host SCSI bus or on said local SCSI bus.

14. A system for allowing more than eight devices to be effectively connected to a single narrow host SCSI bus, the system adapted to enable communications to occur between a host device having a first SCSI port, and a plurality of target devices, each having a SCSI port, the system comprising:

a host SCSI bus connected to the first SCSI port of the host device, the host device having a first host bus SCSI ID number used to identify the host device on said host SCSI bus;

a local SCSI bus connected to the SCSI ports of the plurality of target devices;

Corona means having a second SCSI port and a third SCSI port, for transferring the communications between the host device and one of the plurality of target devices selected by the host device, said Corona means connected to said host SCSI bus at said second SCSI port and to said local SCSI bus at said third SCSI port, said Corona means having a second host bus SCSI ID number used to identify said Corona means on said host SCSI bus and a first local SCSI ID number used to identify said Corona means on said local SCSI bus, and for converting a SCSI logical unit number received from the host device to a second local bus SCSI ID number, said second local bus SCSI ID number identifying said selected target device on said local SCSI bus to establish communications between the host device and said selected target device; and

a controller connected to said Corona means for supporting and controlling said Corona means during SCSI operations between said host SCSI bus and said local SCSI bus, wherein said system is capable of transferring data between said host SCSI bus and said local SCSI bus in either asynchronous, synchronous or fast synchronous mode.

15. The system according to claim 14, wherein said controller performs data mode conversion control during data transfers between said host SCSI bus and said local SCSI bus.

16. A method for allowing more than eight units on a host SCSI bus to transfer communications between a host device having a first SCSI port and a selected on of a plurality of target devices, each having a SCSI port, the host device connected to the host SCSI bus at the first SCSI port and having a first host bus SCSI ID number used to identify the host device on the host SCSI bus, the system having a Corona device having a second SCSI port and a third SCSI port, the Corona device connected to the host SCSI bus at the second SCSI port and to a local SCSI bus at the third SCSI port, and the plurality of target devices connected to a local SCSI bus, the method comprising:

a) selecting the host SCSI bus type;

b) designating a second or multiple host bus SCSI IDs identifying the Corona device on the host SCSI bus;

c) checking to determine whether an operation will be in repeater or LUN operation mode;

d) if the Corona device is not already configured to a desired operation mode, reconfiguring the Corona device for a desired repeater or LUN operation mode;

e) performing a first select cycle to enable the host device to select the Corona device at said designated second host bus SCSI ID number;

f) converting a SCSI logical unit number received from the host device on the host SCSI bus to a corresponding first local SCSI ID number associated with the selected target device on the local SCSI bus;

g) checking to determine an agreed upon data transfer mode;

h) if the Corona device is not already configured to the agreed upon data transfer mode, reconfiguring the Corona device to the agreed upon data transfer mode;

i) performing a second select cycle to enable the Corona device to select the selected target device at said first local SCSI ID number; and

j) connecting the host device and the selected target device through the Corona device to establish communications between the host device and the selected target device.

17. The method according to claim 16, further comprising the steps of:

a) detecting error condition on either said host SCSI bus or said local SCSI bus; and

b) reporting any of said error conditions on either said host SCSI bus or said local SCSI bus to said host device.

18. The method according to claim 16, further comprising the steps of:

a) designating a second local bus SCSI ID number identifying the Corona device on the local SCSI bus;

b) performing a first reselect cycle to enable the selected target device to select the Corona device at said designated local bus SCSI ID number;

c) converting said first local SCSI ID number associated with the selected target device on the local SCSI bus to said SCSI logical unit number;

d) checking to determine the agreed to data transfer mode;

e) if the Corona device is not already configured to the agreed to data transfer mode, reconfiguring the Corona device to the agreed to data transfer mode;

f) performing a second reselect cycle to enable the Corona device to select the host device at the first host SCSI ID number; and

g) connecting the host device and the selected target device through the Corona device to permit communications to take place between the host device and the selected target device.

19. The method according to claim 18, further comprising the steps of:

a) detecting error condition on either said host SCSI bus or said local SCSI bus; and

b) reporting any of said error conditions on either said host SCSI bus or said local SCSI bus to said host device.