Operating instructions

16-2
SCSI REFERENCE 1012975
CHAPTER 16—RECEIVE DIAGNOSTIC RESULTS (1Ch)
16.2 WHAT YOU SEND TO THE AUTOLOADER
Bytes 03 and 04 – Allocation Length
This field specifies the number of bytes that the initiator has allocated for the
return of RECEIVE DIAGNOSTICS RESULTS data. The autoloader returns
only one diagnostic page per command.
Table 16-1 lists the diagnostic pages returned by the RECEIVE DIAGNOSTIC
command and their maximum page lengths. Setting the Allocation Length to 0
indicates that no diagnostic data will be returned and is not an error.
The autoloader terminates the Data In phase when the number of bytes
specified in the Allocation Length field has been transferred or when all
available data has been transferred to the initiator, whichever is less.
16.3 WHAT THE AUTOLOADER RETURNS
When the autoloader receives a RECEIVE DIAGNOSTIC RESULTS command,
it returns the results of the previous SEND DIAGNOSTIC command. Each
page of the diagnostic data begins with a four-byte Diagnostic Parameter
Header (bytes 00 through 03), followed by the diagnostic parameters for that
page. The Diagnostic Parameter Header indicates the page code for the
diagnostic parameter data being returned and indicates the total length of the
data to follow.
Byte 00 – Page Code
This field identifies the page code of the diagnostic for which the tape drive is
returning data. Table 16-1 lists the valid page codes.
Table 16-1 Maximum page length of each supported RECEIVE DIAGNOSTIC page
Page Code Page Name Maximum Length
a
a. This maximum length value includes the four-byte Diagnostic Parameter header sent with each page.
00h Supported Diagnostic Pages page 20h (32 bytes)
F0h Self Test page 400h (1,024 bytes)
FFh No Diagnostic Results Available page 04h (4 bytes)
Bit
Byte
7 6 5 4 3 2 1 0
00 Page Code
01 Reserved
02 (MSB)
Page Length
(LSB)
03