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Format
Address Bus
Request
{I
0
7 8
1718
23
Not Used
I
Channel Number
of Device·
Cycle
0
9 10
15
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Data Bus
Function
Loads, for the referenced device, the interrupt
level and the channel number of the CP to which
subsequent interrupts should be sent. The level
number is a 6-bit quantity and is positioned on the
data bus as illustrated. Bits 0-9 of the data bus
contain the channel number of the CP loading the
interrupt level. If an interrupt level of zero is
loaded, the subsystem will not generate or save
interrupts for any events that occur while the inter-
rupt level is zero. For example, if the attention bit in
Status Word 1 is set to one with a stored interrupt
level of zero, the subsystem will not generate an
interrupt on the bus. The interrupt level is set to
zero whenever the subsystem is initialized.
Command
Output Task Word
Function Code
07
Format
Address Bus
o
7 8
{
I
Not Used
I
Channel Number
Request Cycle
Data Bus
o
7 8
15
I
Comma~d
Code
I
RFU
I
Function
10000000 - Rewind
11000000 - Rewind and Unload
00001 000 - Forward-Space Block
00000100 - Back-Space Block
00011000 - Forward-Space Tape Mark
00010100 - Back-Space Tape Mark
00001001 - Read Forward
00000101 - RFU
00101000 - Erase
00111010 - Write Tape Mark
00101011 - Write
00000000 - No Operation
1718
23
Outputs a Task Word to the referenced channel.
The coding bits 0-7, illustrated above, represent the
operations that are to be performed. When this com-
mand is accepted, the channel enters the Busy state.
All configuration, addresses and range information
must be loaded prior to execution of this command.
The direction of data transfer indicated by the low-
order bit of the most recent Output Address com-
mand must agree with the direction of transfer
(read or write) specified by command code of the
Output Task Word.
If
it does not, Status Word 1
bit 11 Operation Check will be set and a normal
termination of the command without data transfer
and tape motion will result. These commands
addressed to a device not in the online state result in
PROGRAMMING
2-6
the setting of an Operation Check bit prior to a
normal termination of the order.
• Rewind - This command rewinds the tape to
the BOT marker if the most recent Output
Task command was not a "write order" (Write,
Write Tape Mark, Erase). If otherwise, an
erase in the forward direction over approx-
imately one inch of tape precedes the rewind
operation. The drive remains in the Busy state
until the completion of the rewind operation or
the setting of a Time Out check. The sub-
sequent ten commands will be NAKed.
If
the
tape on the drive is at BOT when this order is
issued, tape motion is not initiated and a
normal termination of the order results. Note
that the rewinding of a drive via the REWIND
button on the drive does not put the device in
the Busy state but activates rewinding (Status
Word 2 bit 1), which affects the states of the
Device Ready and Attention bits of Status
Word 1. When the manually initiated rewind
is complete, the Rewinding status condition
resets, Device Ready changes state, and the
Attention bit is set again.
Note:
A rewind of tape without any erase
operation may be initiated man-
ually via the REWIND button.
• Rewind and Unload - This command imple-
ments a Rewind command and, following
detection of the BOT marker, activates the
drive's unload sequence prior to termination
of the order. If the tape on the drive is at BOT
when this command is issued, then only the
unload sequence is initiated prior to termina-
tion of the command. The unload sequence
puts the selected tape device into the oftline
state, extinguishes the online indicator and
moves tape in the reverse direction until it is
wound off the take-up reel. The tape drive can
manually be placed into the online state only
from the device control panel.
Note:
A tape drive may be put in the oftline
state without any erase action or
tape motion manually via the
ONLINE button.
• Forward-Space Block -
This command
results in the drive spacing 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
forward-space block operation. The order
terminates when tape is positioned in the next
interblock gap or as a result of a Time Out
Check.
• Backspace Block - This command results in
the drive spacing back over the previous block
on tape if the most recent Output Task com-
CFIO
'-
. ./
/
./
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