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|  MIL-D-81347C(AS)
3.5.2.4.1.3.3.2.4
Write Function - The MTT can be programmed to write forward
one record at 200, 555.5 or 800 bits per inch using either odd or even Lateral Parity.
Write Function Operation - When the MTC detects a Write
3.5.2.4.1.3.3.2.4.1
Function, it shall cause the selected transport to move the tape forward at 75 inches per second and
record an Interrecord Gap. A signal is then placed on the computer Output Data Request line. The
computer will then respond with the first data word. The MTC shall disassemble each word into five
6-bit characters, generate a Lateral Parity bit, and transfer the seven-bits to the selected transport
for recording on tape according to the density selected. When the recorded frame passes over the
read head, it is checked for Lateral Parity. If a Lateral Parity error is detected, upon completion of
the function, a Parity Error is transmitted to the computer. If no error occurs during recording, the
process will continue until the computer no longer acknowledges the Output Data Request within the
time allotted for another word to be disassembled and written. The above procedure shall be repeated
until the end of the first record; since the data is written on the tape in the form of records, a new
External Function will be required for each record written.
Write Function Conditions - Conditions that may occur during a
3.5.2.4.1.3.3.2.4.2
Write Function and shall be indicated by an External Interrupt and a Status word are as follows:
(1) Normal Completion
(2) Rewinding
(3) End of Tape Warning
(4) Low Tape Warning
(5) Write Lockout
(6) Illegal Instruction
(7) Improper Frame Count
(8) Fault
(9) Lateral Parity Error
(lo) Longitudinal Parity Error
(11) Timing Error
(12) Illegal Operation
Write Function Termination - The Write Function word will be
3.5.2.4.1.3.3.2.4.3
followed by at least one Data word. (If no Data words are transferred, an Output Timing Error shall
be generated. ) Each Data word to be written in a record must be received by the MTC within a pre-
determined amount of time such that the spacing between the corresponding bits of adjacent characters
within the record shall be a nominal distance of 200, 555.5 and 800 characters per inch at 75 inches
per second. Otherwise the MTC shall assume an "End of Write. " Longitudinal Parity shall then be
written after an appropriate delay and the recording process terminated. Tape motion shall be
stopped after part of the IRG is written on the tape. The MTC shall place a "Normal Completion" or
appropriate Error Status word on the computer input lines and send an External Interrupt to the com-
puter. Data received after the termination but before a new Function word shall be considered an
Output Timing Error and shall not be recorded.
Write XIRG - The selected MTT shall record an Extended Inter-
3.5.2.4.1.3.3.2.5
record Gap of 3-1/2 inches instead of the normal 3/4 inch IRG preceding a normal Write portion
of the operation. If no data is transferred from the computer for recording, the XIRG will be on the
tape and an Output Timing Error shall be generated. The Status word sent to the computer shall con-
tain MTC status and all error indications detected in a Normal Write Operation.
102
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