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|  MIL-D-81347C(AS)
Search File Forward - The selected MTT shall read records from
3.5.2.4.1.3.3.2.12
the tape in the forward direction and compare the first word of each tape record with an Identifier word,
which is transmitted from the computer to the M'TC by a one-word output buffer. When a compare
occurs, that Found record shall be transmitted to the computer as in a Normal Read.
Search File Operation - The Function that specified a Search File
3.5.2.4.1.3.3.2.12.1
will be followed by an Identifier word, of 30-bits, which may be any configuration of bits except that
bits 24 through 27 may not be zero simultaneously. The Search portion OF the Search File operation
compares the first word of the record with the ldentifier word. If a find is not made, the MTC shall
move on to the next record and compare the first word of that record with the Identifier word. This
process shall continue until a find is made, an error occurs, the search is terminated or a tape mark
occurs. When a find is made. the MTC shall perform a Read Type operation, which shall be the same
as a Normal Read operation. The Read operation shall begin with the Identifier word and continue until
the end of the record.
Search File Conditions - Conditions which may occur during a
3.5.2.4.1.3.3.2.12.2
Search File function shall be indiceted by an External Interrupt. These conditions are identical to the
read conditions.
Search File Termination - If the MTC does not receive the Identi-
3.5.2.4.1.3.3.2.12.3
fier word from the computer before it starts searching a record, an Output Timing Error shall be
generated. The Search File operation shall be terminated whenever a parity or timing error is gene-
rated. A Tape Mark and a Normal Completion shall also terminate the Search File operation. When
the tape motion is stopped due to an error, the tape shall be positioned in the IRG after the records in
which the error occurred.
Space File - The MTC shall cause the selected transport to move
3.5.2.4.1.3.3.2.13
the tape in the Forward direction to the IRG beyond the next Tape Mark and shall send a normal com-
pletion Status Code to the computer when the function is complete.
Read Function - The MTC can be programmed to read in the
3.5.2.4.1.3.3.2.14
forward direction only one record at a time.
Read Function Operation - To read from a selected tape, the
3.5.2.4.1.3.3.2.14.1
program will issue a Read Function for each record; however, the computer may stop accepting data
at any point within the record, or accept none of the information. The computer must sample the
input lines and acknowledge each input Data Request within a specified time for each density, or words
will be lost. If the computer fails to sample the input lines and acknowledge the Input Data Request
within this allotted time, an Input Timing Error shall occur and the MTC shall cease the transfer of
data to the computer for the remainder of the record. Following detection of "End of Record", the
MTC shall set the Input Timing Error Status word on the input lines and generate an External Interrupt
to the computer.
Read Function Condition - Conditions that may occur during a
3.5.2.4.1.3.3.2.14.2
Read Function shall be Indicated by an External Interrupt. They are as follows:
(1) Normal Completion
.
(2) Rewinding
(3) End of File
(4) End of Tape Warning
(5)
Load Point
(6) Low Tape Warning
(7) Illegal Instruction
104
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