trol unit contains a pending channel end or control
unit end for the addressed device. The csw unit
status field contains the busy bit, identifies the inter
ruption condition, and may contain other bits pro
vided by the device or control unit. The interruption
condition is cleared. The channel-status field contains
zeros.
3. TheI/O device or the control unit is executing a
previously initiated operation, or the control unit has
pending channel end or control unit end for a device
other than the one addressed. The csw unit-status
field contains the busy bit or, if the control unit is
busy, the busy and status-modifier bits. The channel
status field contains zeros.
4. TheI/O device or channel detected an equip
ment or programming error during execution of the
instruction. The channel-end and busy bits are off,
unless the error was detected after the device was
selected and was found to be busy, in which case the
busy bit, as well as any bits indicating pending inter
ruption conditions, are on. The interruption conditions
indicated in the csw have been cleared at the device.
The csw identifies the error condition. TheI/O op
eration has not been initiated. No interruption condi
tions are generated at theI/O device or subchannel.
Resulting Condition Code:
oI/O operation initiated and channel proceed-
ing with its execution
1 csw stored
2Channel or sub channel busy
3 Not operationalProgram Interruptions: Privileged operation.
Programming Note
When a programming error occurs and the addressed
device contains an interruption condition, with the
channel and subchannel in the available state,START I/O mayor may not clear the interruption condition,
depending on the type of error and the model. If the
instruction has caused the device to be interrogated,
as indicated by the presence of the busy bit in the
csw, the interruption condition has been cleared, and
the csw contains program check, as well as the status
from the device.
TestI/O rio 51
9D 78 1516 1920 31
The state of the addressed channel, subchannel, and
device is indicated by setting the condition code in
the psw and, under certain conditions, by storing the
csw. Pending interruption conditions may be cleared.
The instructionTEST I/O is executed only when the CPU is in the supervisor state.
Bit positions 21-31 of the sum formed by the addi
tion of the content of register Bl and the content of
the Dl field identify the channel, subchannel, andI/O device to which the instruction applies.
When any of the following conditions is detected,TEST I/O causes the csw at location 64 to be stored.
The content of the csw pertains to theI/O device ad
dressed by the instruction.
1. The subchannel contains a pending interruption
condition due to a terminated operation at the ad
dressed device. The interruption condition is cleared.
The protection key, command address, and count
fields contain the final values for theI/O operation,
and the status may include other bits provided by
the channel and the device. The interruption condi
tion in the subchannel is not cleared, and the csw is
not stored if the interruption condition is associated
with an operation on a device other than the one
addressed.
2. TheI/O device contains a pending interruption
condition due to device end or attention, or the con
trol unit contains a pending channel end or control
unit end for the addressed device. The csw unit-status
field identifies the interruption condition and may
contain other bits provided by the device or control
unit. The interruption condition is cleared. The busy
bit in the csw is off. The other fields of the csw con
tain zeros.
3. TheI/O device or the control unit is executing a
previously initiated operation or the control unit has
pending channel end or control unit end for a device
other than the one addressed. The csw unit-status
field contains the busy bit or, if the control unit is
busy, the busy and status-modifier bits.Other fields
of the csw contain zeros.
4. TheI/O device or channel detected an equip
ment error during execution of the instruction. The
csw identifies the error condition. No interruption
conditions are generated at theI/O device or the sub
channel.
WhenTEST I/O is used to clear an interruption con
dition from the subchannel and the channel has not
yet accepted the condition from the device, the in
struction causes the device to be selected and the
interruption condition in the device to be reset. Dur
ing certainI/O operations, some types of devices can
not provide their current status in response toTEST I/O. The tape control unit, for example, is in such a
state when it has provided the channel-end condition
and is executing the backspace-file operation. WhenTEST I/O is issued to a control unit in such a state, the
unit-status field of the csw contains the busy andInput/Output Operations 93
unit end for the addressed device. The csw unit
status field contains the busy bit, identifies the inter
ruption condition, and may contain other bits pro
vided by the device or control unit. The interruption
condition is cleared. The channel-status field contains
zeros.
3. The
previously initiated operation, or the control unit has
pending channel end or control unit end for a device
other than the one addressed. The csw unit-status
field contains the busy bit or, if the control unit is
busy, the busy and status-modifier bits. The channel
status field contains zeros.
4. The
ment or programming error during execution of the
instruction. The channel-end and busy bits are off,
unless the error was detected after the device was
selected and was found to be busy, in which case the
busy bit, as well as any bits indicating pending inter
ruption conditions, are on. The interruption conditions
indicated in the csw have been cleared at the device.
The csw identifies the error condition. The
eration has not been initiated. No interruption condi
tions are generated at the
Resulting Condition Code:
o
ing with its execution
1 csw stored
2
3 Not operational
Programming Note
When a programming error occurs and the addressed
device contains an interruption condition, with the
channel and subchannel in the available state,
depending on the type of error and the model. If the
instruction has caused the device to be interrogated,
as indicated by the presence of the busy bit in the
csw, the interruption condition has been cleared, and
the csw contains program check, as well as the status
from the device.
Test
9D
The state of the addressed channel, subchannel, and
device is indicated by setting the condition code in
the psw and, under certain conditions, by storing the
csw. Pending interruption conditions may be cleared.
The instruction
Bit positions 21-31 of the sum formed by the addi
tion of the content of register Bl and the content of
the Dl field identify the channel, subchannel, and
When any of the following conditions is detected,
The content of the csw pertains to the
dressed by the instruction.
1. The subchannel contains a pending interruption
condition due to a terminated operation at the ad
dressed device. The interruption condition is cleared.
The protection key, command address, and count
fields contain the final values for the
and the status may include other bits provided by
the channel and the device. The interruption condi
tion in the subchannel is not cleared, and the csw is
not stored if the interruption condition is associated
with an operation on a device other than the one
addressed.
2. The
condition due to device end or attention, or the con
trol unit contains a pending channel end or control
unit end for the addressed device. The csw unit-status
field identifies the interruption condition and may
contain other bits provided by the device or control
unit. The interruption condition is cleared. The busy
bit in the csw is off. The other fields of the csw con
tain zeros.
3. The
previously initiated operation or the control unit has
pending channel end or control unit end for a device
other than the one addressed. The csw unit-status
field contains the busy bit or, if the control unit is
busy, the busy and status-modifier bits.
of the csw contain zeros.
4. The
ment error during execution of the instruction. The
csw identifies the error condition. No interruption
conditions are generated at the
channel.
When
dition from the subchannel and the channel has not
yet accepted the condition from the device, the in
struction causes the device to be selected and the
interruption condition in the device to be reset. Dur
ing certain
not provide their current status in response to
state when it has provided the channel-end condition
and is executing the backspace-file operation. When
unit-status field of the csw contains the busy and