Black Box SC120A-R2, SC121A manual General Hardware Description

2 X 2 SCSI MATRIX SWITCH

2.3.2GENERAL HARDWARE DESCRIPTION

The 2 x 2 SCSI Matrix Switch’s rear panel identifies each of the independent SCSI ports. SCSI ports A and B have two daisychained connectors per port and SCSI ports 1 and 2 have single connectors for installation of SCSI devices. You can install the SCSI Switch at any point on the SCSI bus.

Each port has internal termination that can be turned on or off from the LCD panel. External “terminator power” (TERMPWR) for devices and terminators are provided by internal resettable fuses.

The SCSI Switch does not require a device ID and is completely transparent to all computers and peripherals on the SCSI bus. No additional software is needed for installation and operation. A universal switching power supply automatically adapts to input voltages between 95 VAC and 260 VAC.

2.3.3ULTRA2 SCSI COMPATIBILITY

The SCSI Switch supports Ultra2 SCSI, 80-MBps (wide) SCSI host adapters, computers, and peripherals in asynchronous and synchronous mode. (SC120A-R2 also supports Ultra160 SCSI, 160-MBps devices.) The SCSI Switch conforms to ANSI X3.131 and X3T9.2 specifications for single-ended devices. Disconnect and reselect functions are fully supported to ensure complete SCSI compatibility.

2.3.4SCSI SWITCH INSTALLATION

Ports A and B are fully bidirectional to ports 1 and 2 (see Figures 2-1 through 2-3). You determine where to connect computers, host adapters, and peripherals. In general, if daisychained ports are required for connection to external peripherals, use ports A or B.

The LCD panel is used to select port connections and enable or disable each internal SCSI port terminator. Refer to Chapter 4 for complete instructions on operating the LCD keypad.

You can selectively enable or disable any internal terminator to meet system configurations and requirements.

NOTES

1.For proper operation of any SCSI bus, there must not be a “hanging” line or cable. Termination should be enabled on active SCSI ports that are not connected through to another port.

2.Connections can be made to either connector on the appropriate port.

3.In Figures 2-1 and 2-3, “Term” shows where terminators should be installed.

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