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delay corresponding to a three-character spacing and then send a Write Reset command to the MTT
to Write the longitudinal parity bits on the tape. The MTC will then time a delay corresponding to
the "write to read" head spacing. If the instruction has resulted in a Normal Completion, i.e. , no
Lateral or Longitudinal Parity Error, and no End of Tape Warning, the MTC will send an External
Function Request to the computer and wait while the MTC times the' Repeat Instruction Request time
(300 s). If the computer does not respond with an External Function line during the Repeat In-
struction Request time, the MTC will terminate its External Function Request and wait an additional
16 microseconds for the External Function command. If no External Function command is received,
the MTC will initiate the Stop Timing and terminate the Forward and Read commands to the MTT.
If the Interrupt Enable from the computer is a logical "1", the MTC will send an Interrupt to the
computer and transfer the Status word. When the Interrupt is acknowledged and the MTC has com-
pleted the stop time, the MTC will terminate the Write signal and return to the idle state. If the
computer responds to the External Function Request during the Repeat Instruction Request time,
or during the following 16 microseconds, the MTC will set a Continue Condition Status, examine the
new word for a change in Parity, or Density, send an Interrupt to the computer, and transfer the
Status word.
The MTC will sense the Continue condition and time a delay cor-
responding to the specified Interrecord Gap distance without stopping tape motion. During this time
the MTC will complete its function as described above and bypass the idle state to initiate another
Write operation. From this point the operation will continue as if the Instruction originally proceeded
from the idle state.
If the End of Tape Warning is sensed, the MTC will perform the
Instruction for a time approximately equal to 10 inches of tape for data before terminating the In-
struction and sending an Interrupt to the computer. If an Instruction is completed within the 10 inch
segment of tape following the End of Tape Warning, no new Forward Instruction will be executed.
If the Instruction has resulted in a Normal Completion, the MTC
sets EFR for the Repeat Instruction Request time. If the computer does not respond with an EF during
the Repeat Instruction Request time, the MTC resets the EFR and waits approximately 16 micro-
seconds for a late E F from the computer. If there is no EF from the computer during this time, the
MTC initiates the Stop Timing. At this time if the Interrupt Enable is logical "1", the MTC sets the
Interrupt line and transfers the Status word. If Interrupt Enable is a logical "0", the MTC stores the
fact that an Interrupt is needed and waits for the Interrupt Enable to become a logical "l" at which
time an Interrupt is sent.
If the Instruction has resulted in a Normal Completion and the
computer does respond with an E F during the Repeat Instruction Request time, the MTC will send an
Interrupt at the completion of the Repeat Instruction Request time if the Interrupt Enable is a logical
"1". If the Interrupt Enable is a logical "0", no Interrupt is sent and the MTC enters the Instruction.
If the Instruction results in something other than a Normal Com-
pletion, the MTC will not send an EFR during the Repeat Instruction Request time. At the end of this
time an Interrupt is sent to the computer if the Interrupt Enable line is a logic "1". If the Interrupt
Enable line is a logic "O", the fact that an Interrupt is needed is stored and the Interrupt is sent when
the Interrupt Enable line becomes a logical "1".
Read Function - When a Read class of Instruction, Read Record
3.5.2.4.1.6.3
Forward or Read Record Reverse, is received by the MTC and the idle state is normal, the MTC will
send the appropriate direction command and read control signal to the MTT. The MTC will perform
the Instruction for the first character from the MTT. If the End of Tape Warning is sensed, the MTC
will wait for a time equal to ten inches of tape before terminating the Read and sending an Interrupt
to the computer. If the Instruction is completed within the 10 inches of tape following the End of Tape
Warning, no new forward motion Instruction will be executed. The first character from the MTT will
be checked for proper parity and transferred to storage. The MTC will then initiate a delay time de-
termined by the packing density and tape speed and wait for the next character from the MTT. If the
second character is not received within the specified time, the first character may have been the
Longitudinal Parity Character in a Read Reverse or a Tape Mark. The MTC will initiate the delay
time again and wait for the second character. If the first and second characters were Tape Marks,
no more data will be received and the End of File Status condition will be set if both characters are
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