Viper 60s Theory Of Operation And Maintenance Manual page 131

VIPER SCSI COMMANDS
5.26.3 READ DATA BUFFER Header
6 4 3
o
o
Available Length (LSB)
5.26.4 READ DATA BUFFER Header Field Descriptions
The READ DATA BUFFER Header contains four bytes.
• The first two bytes are reserved and set to'zero.
o
• Bytes two and three contain the Available Length or the space available in the
drive buffer. The Available Length for the drive is 56.5 kilobytes.
An Allocation Length of zero indicates a non-transference of READ DATA BUFFER header
and READ DATA RUFFER data. This is not an error condition.
It
is likewise, not an error to
request an Allocation Length less than Viper drives Available Length plus four (for the
header). In that case, the drive returns the requested length, including the four byte header. If
the number of bytes specified in the Allocation Length exceeds the Available Length plus 4 (or
is not modulo 512 plus 4), it is treated as an Illegal Request.
5.26.5 Completion Status
I
gg~:LETI6N i--MES~S~A-GE-l-D-Es-C-RIP-T'~-N
- . -. .
-"~.-'--"-.- "'-~'--'
~Oh
Good Status • The position of the Media is not changed
• Viper drive is ready to accept any appropriate command
drive remains in set mode.
02h Check Condition Extended Sense byte 02
"f
02~h---
- - - -
~e-;dy
- -
~
cartridge is not
in~
in the drive--
---1
04h
-=- - =- _
Hardware Error • Parity error on either jhe SCSI Bus or Viper
dl'iv~
__
~
OSh Illegal Request • The COB contains an invalid bit
• Allocation Length exceeds the E204h
~
___
~
• Allocation Lengt':lls not modulo 512 plus
~
__
Unit Attention
command
I
• Viper drive was Reset prior to accepting this command.
- - -
--~~
- - -
------------~----~
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