Adaptec AHA-2742T User Manual - Page 110

Command Control Block, Command Descriptor Block, Common Command Set, Device Driver, Differential,

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Glossary CDB See Command Descriptor Block Command Control Block A software object prepared by the host microcomputer software for the host adapter to provide it all the control information it needs to execute a SCSI command. Abbreviated CCB. Command Descriptor Block A block of information passed across the SCSI bus to provide the command, parameter, and address information necessary for the target to execute the desired functions. Prepared by the host software and placed in the CCB to be passed to the target by the host adapter. Abbreviated CDB. Common Command Set A de facto standard SCSI command set for communication with fixed disk drives. The Common Command Set (CCS) is the basis for the SCSI-2 command set for all types of peripheral devices. D Device Driver A software program that enables a PC to communicate with peripheral devices such as fixed disk drives and CD-ROM drives. Each kind of device requires a different driver. Device driver programs are stored on a PC's fixed disk and are loaded into memory at boot time. Differential A term referring to the electrical characteristics of the signals used on the SCSI bus interface. Differential signals occupy two conductors with a positive (+) and negative (-) polarity component of the signal. This minimizes the effect of common mode signal noise and allows the SCSI bus to operate reliably over greater distances at a higher speed. Direct Memory Access A mechanism that allows hardware control of the transfer of streams of data to or from the main memory of a computing system. The mechanism may require setup by the host software. After initialization, it automatically sequences the required data transfer and provides the necessary address information. Glossary-5 Adaptec AHA-2740 Series User's Manual Stock Number: 510381-00 / Rev. C (Page G-5) Print Spec Number: 491709-00 Rev C Current Date: 9/1/93 ECN Date: 9/14/93

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CDB
See Command Descriptor Block
Command Control Block
A software object prepared by the host microcomputer software
for the host adapter to provide it all the control information it
needs to execute a SCSI command. Abbreviated CCB.
Command Descriptor Block
A block of information passed across the SCSI bus to provide the
command, parameter, and address information necessary for the
target to execute the desired functions. Prepared by the host soft-
ware and placed in the CCB to be passed to the target by the host
adapter. Abbreviated CDB.
Common Command Set
A de facto standard SCSI command set for communication with
fixed disk drives. The Common Command Set (CCS) is the basis
for the SCSI-2 command set for all types of peripheral devices.
D
Device Driver
A software program that enables a PC to communicate with
peripheral devices such as fixed disk drives and CD-ROM drives.
Each kind of device requires a different driver. Device driver pro-
grams are stored on a PC’s fixed disk and are loaded into memory
at boot time.
Differential
A term referring to the electrical characteristics of the signals
used on the SCSI bus interface. Differential signals occupy two
conductors with a positive (+) and negative (-) polarity component
of the signal. This minimizes the effect of common mode signal
noise and allows the SCSI bus to operate reliably over greater
distances at a higher speed.
Direct Memory Access
A mechanism that allows hardware control of the transfer of
streams of data to or from the main memory of a computing sys-
tem. The mechanism may require setup by the host software.
After initialization, it automatically sequences the required data
transfer and provides the necessary address information.
Adaptec AHA-2740 Series User’s Manual
Stock Number:
510381-00
/
Rev. C
(Page G-5)
Print Spec Number:
491709-00 Rev C
Current Date:
9/1/93
ECN Date:
9/14/93
Glossary
Glossary-5