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decoded as Tape Marks (0001111) or if one is decoded as a Tape Mark and the other has a single bit
error. If the second character is received within the second delay time and is followed by a third
within one delay time, the first character will be discarded since it was the Longitudinal Parity
character. The process of waiting for characters, checking parity and transferring the characters
to storage will continue with the MTC counting the characters received. When five characters have
been received, the MTC will set a full condition. The MTC will send an Input Data Request to the
computer, transfer the Data word, and wait for an Input Acknowledge. If the computer responds
within the word transfer time determined by the packing density, the MTC will reset the Full
Condition. The MTC will set the Full Condition when five more characters have been received
and the process will continue until no more data is received from the MTT or until the computer
does not respond to the Input Data Request within the word transfer time. If the computer does not
respond, the MTC will set the Timing Error Status condition and drop its Input Data Request. In
either event the MTC will continue its operation until no more data characters are received from the
MTT. If the instruction has resulted in a normal completion, the MTC will send an External Function
Request to the computer and wait while the MTC times the Repeat Instruction Request time. If the
computer does not respond with an External Function command during the Repeat Instruction 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 is received, the MTC will initiate the
stop timing and terminate the Forward or Reverse command to the MTT. During this time the MTC
will place the Status word on the data lines and send an Interrupt to the computer. If the Interrupt
Enable from the computer is a logical "1", the MTC will wait for an Input Acknowledge. When the
Interrupt is acknowledged and the MTC has completed the stop time, the MTC will return to the idle
state. If the computer responds to the External Function Request during the Repeat Instruction Re-
quest time or during the following 16 microseconds, the MTC will set a Continue condition, place the
Status word on the input data lines, and send an Interrupt to the computer. The MTC will sense the
Continue condition and initiate the new Instruction without stopping tape motion. During this time
the MTC will complete its function as described above and bypass the idle state to initiate another
Read operation. From this point the operation will continue as if the Instructions originally pro-
ceeded from the idle state.
If the Instruction is a Read Reverse, the MTC will assemble the
characters in the correct order.
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 EFR and waits approximately 16 microseconds
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 In-
terrupt line and transfers the Status word. If the 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 "1" 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 "O"; 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 logical `1". If the Interrupt
Enable line is a logical "O", the fact that an Interrupt is needed is stored and the Interrupt is sent when
the Interrupt Enable line becomes a logical *'1".
Search File Forward - When the Search File Forward instruction
3.5.2.4.1.6.4
is received and the idle state is normal, the MTC will send an External Function Request to the com-
puter and set the MTC full condition. At the same time, the MTC will initiate the same functions that
are performed in the Read operation. If the computer does not respond with an External Function Line
indicating the Identifier word is on the computer output lines before the MTC receives the first data
character from the MTC, the MTC will set the Timing Error Status condition and terminate its Exter-
nal Function Request. The MTC will then wait until the MTC stops receiving data from the MTT, send
an Interrupt to the computer and transfer the Status information to the computer. If the computer does
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