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946261-9701
A failure to verify an ID word results in an ID error status (bit 11) and termination of the read data
operation. When the controller encounters the end of a record but the remaining transfer word
count is
nonzero~
the controller automatically continues reading data on the next sequential record
of the track if it exists. The new record ID is checked before continuation of data gathering.
When the remaining transfer word count is zero but the controller has not encountered the end
of a record, then the controller discontinues transmitting data words across the TILINE bus but
continues to read data from the disk until the end-of-record is encountered so that the eRe
character can be checked before loading status.
When the controller encounters the end of a track and the remaInlng transfer word count is
nonzero, the controller automatically increments the head address to the next track; reads the ID
words for the first sector (00) of that track; verifies the contents of
10
words 1 and 2; stores the
contents of
10
word 3; verifies the eRe character following the
10
words; looks for sync
character and continues reading data from disk and again begins transferring data over the
TILINE bus.
When the controller encounters the end of a cylinder, and the remaining transfer word count is
nonzero, the controller automatically seeks to the next cylinder; selects head address zero for the
new track; reads the ID words for sector 00; verifies the contents of ID words 1 and 2; stores the
contents of ID word 3; verifies the eRe character following the ID words; looks for sync character
and continues to read words from the disk and transfer them to the TILINE bus if transfer inhibit is
not specified.
If
the end-of-cylinder occurs, and the remaining word count is nonzero, the operation
will terminate with unit error and the resultant unit error will be seek incomplete caused by illegal
address interlock ORed with seek incomplete.
3.5.9.4 Write Data Command. For a write data command the controller transfers the number of
specified 16-bit words from the specified TILINE addresses to the specified disk addresses. After
initialization, the controller checks for unit errors by examining disk status (offline, not ready, un-
safe, write protect, seek incomplete); seeks to the specified cylinder; searches for the desired sector
address; reads the ID words; verifies ID words 1 and 2; stores the contents of ID word 3; and verifies
the eRe character following the ID words.
If
the ID words compare, the controller switches to the
write mode and, after a specified delay, starts writing a sync character and data on the disk. If the
ID words fail to compare, the operation is terminated with an ID status error.
Data is written on the disk until the specified number of words has been transferred unless a ter-
minate condition is encountered. When the number of words to be transferred is greater than the
number of words per record, the controller continues to the next sequential record. The next sequen-
tial record starts at the sector number whose value is equal to the beginning sector number of the last
record plus the number of sectors per record.
When the transfer word count is less than the record word count, the controller fills the
remainder of the record with zeros until the record word count has been decremented to zero.
The controller compares the
10
words from its internal registers with the
10
words read from
disk at the specified sector address.
If
the
10
words are identical, the eRe character is checked.
3-13
Digital Systems Division
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