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SCSI INTERFACE
CHAPTER
5
SCSI INTERFACE
5.1 Introduction
The Python DDS-DC DAT drives provide an embedded Small Computer System Interface (SCSI) controller
for communications between the host computer and the DAT drive. The Python drives support the SCSI-1
(ANSI Standard X3.131-1986) or SCSI-2 (ANSI X3T9.2 WORKING DRAFf Revision 10) interfaces.
The factory default interface at power up is for the SCSI-2 interface. (For Python internal drives, the SCSI
interface is selected by S4 on the 8-position DIP switch. See Chapter 3 for more infonnation about this
switch.) The SCSI-2 interface provides a modified MODE SENSE page to control and report on data
compression operations. Data compression can also be enabled and disabled by software (MODE SELECT
command), which overrides the DIP switch setting.
The Python 4322, 4542, and 4352 drives provide a single-ended SCSI connection. This chapter summarizes
the SCSI-1 and SCSI-2 status codes, message codes, and commands. Refer to Chapter 3 for specific SCSI
cabling and connector infonnation.
NOTE:
Refer to the Python Technical Reference Manual (PIN 25356-002, DDS-only) or to the
Python SCSI Manual (PIN 27298-001, available in 1992) for detailed information
about the SCSI interfaces. That manual includes an alphabetically arranged summary
of the Python SCSI commands. Appendix C of this manual provides specific SCSI
information pertaining to data compression.
5.2 SCSI-1 Interface
The SCSI-1 interface for the premium series DAT drives confonns with the ANSI Standard X3.131-1986.
Tables 5-1,5-2, and 5-3 list the Status Codes, Message Codes, and Commands for this interface.
Table 5-1. Status Codes---SCSI-1
4-BITSTATUS CODE
Bits
4
3
2
0
DEFINI110N
0
0
0
0
X
Good Status
0
0
0
1
X
Check Condition
0
1
0
0
X
Busy
1
0
0
0
X
I ntermediate Status
1
0
0
X
Reservation Conflict
5-1
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