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When the subchannel is either working with the
addressed device or interruption-pending with the
addressed device, the CLRIO function causes
condition code 1 to be set and causes the channel
to discontinue the operation with the addressed
device by storing the status of the operation in the
CSW and making the subchannel available. When
the channel is working with the addressed device,
the device is signaled to terminate the current
operation. Some channels may, instead, indicate
busy and cause no channel action.
When any of the following conditions occurs, the
CLRIO function causes the CSW at location 64 to
be stored. The contents of the entire CSW pertain
to the 110 device addressed by the instruction.
1. The channel is available or interruption-
pending, and the subchannel contains an
interruption condition for the addressed device
or is working with the addressed device. The
subchannel-key, command-address, and count
fields describe the state o( the operation at the
time of the execution of the instruction.
2. The channel is working with the addressed
device. The subchannel-key, command-
address, and count fields describe the state of
the operation at the time the instruction is
executed. (Some channels alternatively
indicate busy under this condition.)
3. The channel is working with a device other
than the one addressed, and the sub channel
contains an interruption;"pending condition for
the addressed device or is working with the
addressed device. The subchannel-key,
command-address, and count fields describe the
state of the operation at the time CLEAR 1/0
is executed. (Some channels alternatively
indicate busy under these conditions.)
\
4. The channel detected an equipment error
during the execution of the instruction. The
CSW identifies the error condition. The states
of the channel and the 110 operations in
progress are unpredictable. The limited
channel logout, if stored, indicates a sequence
code of 000.
When CLEAR 110 cannot be executed because
of a pending logout that affects the operational
capability of the channel, a full CSW is stored.
The fields in the CSW are all set to zeros, with the
exception of the logout-pending and channel-
control-check bits, which are set to ones. No
channel logout is associated with this status.
Program Exceptions:
Privileged Operation
Resulting Condition Code:
a
No operation in progress for the addressed
device
1
CSW stored
2
Channel busy
3
Not operational
The condition code set when CLEAR 110 causes
the CLRIO function to be performed is shown 'for
all possible states of the 110 system in the figure
"Condition Codes Set by CLEAR 1/0." The
condition code set when CLEAR 110 causes the
TIO function to be performed is shown for all
possible state of the 110 system in the figure
"Condition Codes Set by TEST 1/0" in the
definition of the instruction TEST 1/0. See the
section "States of the Input/Output System" in this
chapter for a detailed definition of the A, I, W, and
N states.
Chapter 12. Input/Output Operations
12-15
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