Control). See also "Input/Output Device Address-
." mg.
If the addressed device is not installed or has been
logically removed from the control unit, but the as
sociated control unit is operational and the address
has been assigned to the control unit (for example,
access mechanism 7 on the IBM3830 Storage Con
trol thathas only access mechanisms 0-3 installed)
thedevice is said to be not-ready. When an instruc
tion is addressed to a device in the not-ready state,
the control unit responds to the selection and indi
cates unit-check whenever the not-ready state pre
cludes a successful execution of the operation. See"Unit Check. " Inte"uption Pending in Subchannel (AIX): The
addressed channel is available. An interruption con
dition is pending in the addressed subchannel be
cause of the concluding of the portion of the opera
tion involving the use of channel facilities. The sub
channelis in a position to provide information for a
complete CSW. The interruption condition can indi
cate concluding of an operation at the addressedI/O device or at another device on the subchannel. The
state of the addressed device is not significant, ex
cept when TESTI/O is addressed to the device as
sociated with the concluded operation, in which case
the CSW contains status information provided by
thedevice. The state AIX does not occur on the selector
channel.On the selector channel, the existence of an
interruption condition in the sub channel immediately
causesthe channel to assign to this condition the
highest priority forI/O interruptions and, hence,
leads to tlhe state IIX.
Subchannel Working (A WX): The addressed chan
nel is available. The addressed subchannel is execut
ing a previously initiated operation or chain of oper
ations and has not yet received the channel end for
the last operation. The state of the addressed device
is not significant, except when HALTI/O or HALT
DEVICE is issued. During HALTI/O and HALT
DEVICE, the state of the device may be interrogat
ed andwill then be indicated in either the CSW or
the condition code.
The subchannel-working state does not occur on
the selector channel since all operations on the selec
tor channel are executed in the burst mode and
cause the channel to be in the working state
(WWX).
194 System/370Principles of Operation Subchannel Not Operational (ANX): The addressed
channel is available. The addressed sub channel on
the multiplexer channel is not operational. A sub
channel is not operational when it is not provided in
the system. This state cannot occur on the selector
channel.
Interruption Pending in Channel (IXX): The ad
dressed channel is not working and has established
which device will cause the nextI/O interruption
from this channel. The state where the channel con
tains a pending interruption condition is distin
guished only by the instruction TEST CHANNEL.
This instruction does not cause the sub channel andI/O device to be interrogated. The other I/O in
structions, with the exception ofSTORE CHAN
NEL ID, consider the channel available when it con
tains a pending interruption condition. A channel
with a pending interruption condition may be con
sidered to be working by the instructionSTORE CHANNEL ID. When the channel assigns priority
for interruptions among devices, the interruption
condition is preserved in theI/O device or subchan
nel. (See "Interruption Conditions.") Channel Working (WXX): The addressed channel
is operating in the burst mode. In the case of the
multiplexer channel, a burst of bytes is currently
being handled. In the case of the selector channel, an
operation or a chain of operations is currently being
executed, and the channel end for the last operation
has not yet been reached. The states of the ad
dressed device and, in the case of the multiplexer
channel, of the subchannel are not significant. De
pending on the channel type and system model,
TESTI/O and HALT DEVICE may consider the
channel to be available when the channel is working
with a device other than the addressed device.
Channel Not Operational (NXX): The addressed
channel is not operational. A channel is not opera
tional when it is not provided in the system, when
power is off in the channel, or when it is not config
ured to theCPU. The states of the addressed I/O device and sub channel are not significant.
Resetting of the Input/Output System
Two types of resetting can occur in theI/O system:
anI/O system reset and an I/O selective reset. The
response of each type ofI/O device to the two kinds
of reset is specified in the SL and SRL publications
for the device.
.
If the addressed device is not installed or has been
logically removed from the control unit, but the as
sociated control unit is operational and the address
has been assigned to the control unit (for example,
access mechanism 7 on the IBM
trol that
the
tion is addressed to a device in the not-ready state,
the control unit responds to the selection and indi
cates unit-check whenever the not-ready state pre
cludes a successful execution of the operation. See
addressed channel is available. An interruption con
dition is pending in the addressed subchannel be
cause of the concluding of the portion of the opera
tion involving the use of channel facilities. The sub
channel
complete CSW. The interruption condition can indi
cate concluding of an operation at the addressed
state of the addressed device is not significant, ex
cept when TEST
sociated with the concluded operation, in which case
the CSW contains status information provided by
the
channel.
interruption condition in the sub channel immediately
causes
highest priority for
leads to tlhe state IIX.
Subchannel Working (A WX): The addressed chan
nel is available. The addressed subchannel is execut
ing a previously initiated operation or chain of oper
ations and has not yet received the channel end for
the last operation. The state of the addressed device
is not significant, except when HALT
DEVICE is issued. During HALT
DEVICE, the state of the device may be interrogat
ed and
the condition code.
The subchannel-working state does not occur on
the selector channel since all operations on the selec
tor channel are executed in the burst mode and
cause the channel to be in the working state
(WWX).
194 System/370
channel is available. The addressed sub channel on
the multiplexer channel is not operational. A sub
channel is not operational when it is not provided in
the system. This state cannot occur on the selector
channel.
Interruption Pending in Channel (IXX): The ad
dressed channel is not working and has established
which device will cause the next
from this channel. The state where the channel con
tains a pending interruption condition is distin
guished only by the instruction TEST CHANNEL.
This instruction does not cause the sub channel and
structions, with the exception of
NEL ID, consider the channel available when it con
tains a pending interruption condition. A channel
with a pending interruption condition may be con
sidered to be working by the instruction
for interruptions among devices, the interruption
condition is preserved in the
nel. (See "Interruption Conditions.
is operating in the burst mode. In the case of the
multiplexer channel, a burst of bytes is currently
being handled. In the case of the selector channel, an
operation or a chain of operations is currently being
executed, and the channel end for the last operation
has not yet been reached. The states of the ad
dressed device and, in the case of the multiplexer
channel, of the subchannel are not significant. De
pending on the channel type and system model,
TEST
channel to be available when the channel is working
with a device other than the addressed device.
Channel Not Operational (NXX): The addressed
channel is not operational. A channel is not opera
tional when it is not provided in the system, when
power is off in the channel, or when it is not config
ured to the
Resetting of the Input/Output System
Two types of resetting can occur in the
an
response of each type of
of reset is specified in the SL and SRL publications
for the device.