The count field
with an operation terminated by HALT
Termination
the available state and causes
be stored. The validity of the
When the
operation at a subchannel in the
interruption-pending state, up to three
subsequent interruption conditions
related to the operation can occur.
Since the
subchannel to be made available, these
interruption conditions will result in
only the status portion of the
indicated.
The first interruption condition arises
when channel end is signaled to a selec
tor or block-multiplexer channel. This
occurs only when the interruption
pending state of the subchannel at the
execution of
previous execution of HALT
tions arise when control-unit end, if
any, and device end are signaled to the
channel.
When the
operation at a subchannel in the working
state, up to four subsequent inter
ruption conditions related to the opera
tion can occur. For all of these
conditions, only the status portion of
the
The first interruption condition arises
on certain channels when the terminated
operation was in the midst of data
transfer. Since the device is not
signaled to terminate the operation
during the execution of the
tion unless the channel is working with
the addressed device when the instruc
tion is received, the device may,
subsequent to execution of the
transfer. The channel responds by
signaling the device to terminate data
transfer. Depending on the channel, the
need to signal the device to terminate
data transfer may be ignored or may be
considered an interface-control check
which creates an interruption condition.
unit status, is indicated in the
occur if channel-end status is received
from the device. The third and fourth
conditions may occur if control-unit
end, andlor device end are presented to
the channel. In these three cases, only
unit status is indicated in the
nel.
When
nated by the
field; either zeros, if the channel has
not attempted to initiate the operation
at the device, or the last status
received from the device in the unit
status field; zeros in the channel
status field; and the deferred condition
code is 1. If the unit status is not
zeros, the busy bit is included.
When
having
execution, the suspended channel-program
execution is terminated, condition code
1 is set, and
in the unit-status field and channel
status field. The command-address field
contains the address of the
the S flag, plus 8.
Termination
channel, and system reset is signaled to
all
channel.
channel to conclude operations in all
subchannels. Status information and all
interruption conditions in all subchan
nels are reset, and all operational
subchannels are placed in the available
state.
Termination Due to Equipment Malfunction
When channel-equipment malfunctioning is
detected or invalid signals are received
from a device, the recovery procedure
and the subsequent states of the
subchannels and devices on the channel
depend on the type of error and on the
model. Normally, the program is alerted
to the termination by an
ruption condition, and the associated
interface-control check. However, when
the nature of the malfunction prevents
generation of an
tion, a machine-check interruption
condition is created, and a
stored. A malfunction may cause the
channel to perform
or generate the halt signal.