Honeywell MTU9104 Operation Manual page 14

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mand was not a "write order." If otherwise, an
erase in the forward direction over approx-
imately one inch precedes the backspace block
operation. The order terminates when tape is
positioned in the previous interblock gap, or
when the tape is positioned at BOT, or as a
result of a Time Out Check. If this command is
issued when the tape is positioned at BOT,
tape motion is not initiated and the order is
terminated.
• Forward-Space Tape Mark - This command
results in the drive spacing forward over one
or more blocks until a Tape Mark or EOT
status is detected on tape if the most recent
Output Task command was not a "write
order." If otherwise, an erase in the forward
direction over approximately one inch
precedes the forward-space tape mark opera-
tion. The command terminates when tape is
positioned in the interblock gap following the
block containing a Tape Mark or a data block
when EOT (Status Word 1 bit 7) is set or as a
result of a Time Out Check.
• Backspace Tape Mark -
This command
results in the drive spacing back over one or
more blocks until a tape mark is detected on
tape if the most recent Output Task command
was not a "write order." If otherwise, an erase
in the forward direction over approximately
one inch precedes the backspace tape mark
operation. The command terminates when
the tape is positioned in the interblock gap
preceding the block containing the tape mark
or when the tape is positioned at BOT or as a
result of a Time Out Check. If this order is
issued when the tape is positioned at BOT,
tape motion is not initiated and a normal
termination of the order follows.
• Read Forward - This command results in the
drive reading forward over the next block on
tape if the most recent Output Task command
was not a "write order." If otherwise, an erase
in the forward direction over approximately
one inch precedes the read forward operation.
The order terminates when the tape is
positioned in the next interblock gap or as a
result of a Time Out Check. The format of the
data transferred from tape to memory is a
function of the stored Configuration Word. In
addition to reading data, vertical parity,
longitudinal parity, and the cyclic redundancy
check character are read and integrity checks
are made .
• Erase - This command results in the drive
erasing tape in the forward direction pro-
ducing a 2-inch gap on the tape, if the most
recent Output Task command was a "write
order." If otherwise, an erase in the forward
direction over approximately two· inches
precedes the normal 2-inch erase operation.
The channel of the device remains busy for the
PROGRAMMING
2-7
duration of the erase command and termi-
nates normally.
• Write Tape Mark - This command results
in
the drive erasing tape in the forward direction
producing a 2-inch gap on the tape followed by
the recording of a Tape Mark block if the most
recent Output Task command was a "write
order." If otherwise, an erase in the forward
direction over approximately two inches
precedes the write tape mark operation (2-
inch erase plus write tape mark block). The
tape mark format for 9-track tape is shown in
Figure 2-4. An attempt to write a Tape Mark
Block on a tape unit in Write Protect results in
no tape motion initiated or block written and
the activation of the Operation Check bit of
Status Word 1. The order terminates when the
tape is positioned in the gap beyond the Tape
Mark Block.
• Write - This command results in the drive
writing, in the forward direction, a data block
of the format, and equal to or greater than the
minimum block length allowed, as specified
by the Configuration Word most recently
issued to this addressed channel if the most
recent Output Task command was a "write
order." If otherwise, an erase in the forward
direction over approximately two inches
precedes the write operation. In addition to
writing data, vertical parity, longitudinal
parity, and a cyclic redundancy check charac-
ter (9-track only) are written in the data block
and integrity checks are made. An attempt to
write a data block of less than the minimum
length or to write to a drive in Write Protect
results in no data transfer, no tape motion
initiated, and the activation of the Operation
Check bit of Status Word 1. The order
terminates when the tape is positioned in the
gap beyond the last data block written.
• No Operation - This command or Output
Task command code results in no data trans-
fer, no tape motion initiated, the normal reset
of Status Word bits upon reception of an Out-
put Task command, and a normal termination
of the command.
Command Output Control Word
Function Code 01
Format
Request
Cycle
Address Bus
o
7 8
I
Not Used
I
Channel Number
o
1 234 15
III I II
RFU
i i
1 0 0 0 - Initialize
o
I 0 0 - Stop I/O
o
0 I 0 - Test Mode
1718 23
CFIO