Upon Termination
When
of Operation at
During By I/O Subchannel Sub- Control I/O Command By SIO By By HID Inter- Status
When I/O Is Idle is Working channel Unit Device Chaining or SIOF ByTIO CLRIO+ or HDV ruption
Attention
Status modifier C* Control unit end C* Busy Channel end C* C*H Device end C* Unit check C C C Unit exception
Program-controlled
interruption C* C C C* Incorrect length C C Program check C C Protection check C C Channel data check C C Channel control check C* C* C* C* I nterface control check C* C* C* C* Chaining check C C Deferred condo code 1
Deferred condo code 3
Explanation: C S The channel or device can create or present the status
condition at the indicated time. A CSW or its status
portion is not necessarily stored at this time.
Conditions such as channel end or device end are
created at the indicated time. Other conditions may
have been created previously, but are made accessible to
the program only at the indicated time. Examples of
such conditions are program check and channel data
check, which are detected while data is transferred, but
are made available to the program only with channel end,
unless the PCI flag or equipment malfunctioning have
caused an interruption condition to be generated earlier.
The status indication is stored in the CSW at the
indicated time.
An appearing alone indicates that the condition has
been created previously. The letter.f. appearing with the indicates that the status condition did not necessarily
exist previously in the form that causes the program to be
alerted, and may have been created by the I/O instruetion
or I/O interruption. For example, equipment malfunctioning may be detected during an I/O interruption, causing
channel or interface control check to be indicated; or a
device such as the 2702 may signal the control-un it-busy
condition in response to interrogation by an I/O instruction,
causing status modifier, busy, and control unit end to be
indicated in the CSW. Contents of the CSW Status Fields
the CPU to which the channel is configured. The
information stored by the STORE CHANNEL ID
instruction implies whether the IOEL is used and, if
it is used, specifies the maximum full-channel-logout
length. C* C C* C C C* C* #
H
+ C* S S S S C CS CS S CS S CS CS S CS S C CS CS S CS S C*+ CS+ S S S C+ CS+ S S S C* CS CS S CS C* CS S S S C CS S S S S S S C* CS S S S C* CS S S S S S S C* CS CS CS CS CS C* CS CS CS CS CS S S S C*# S S S C*# S S S The status condition generates an interruption condition. Channel end and device end do not result in interruption
conditions when command chaining is specified and no
unusual conditions have been detected.
This indication is created at the indicated time only by
an immediate operation. Applies only to SIOF. When an operation on the selector channel has been
concluded by HALT DEVICE or HALT I/O, or an
operation has been concluded by CLEAR I/O, channel
end indicates the concluding of the data-handling portion
of the operation at the control unit.
The entries in this column apply only when the CLRIO function is executed. When CLEAR I/O is executed as
TEST I/O, the entries in the TIO column apply. 110 Communications Area
Reallocations 160-191 of the CPU to which the
channel is configured comprise a permanently as­
signed area of main storage used for I/O, designated
the I/O communications area (lOCA). Input/Output Operations 239

160 164
168 Channel 10 172 I 10El Pointer 176 Limited Channel logout (lCU 180 1000000001 I/O AddrElsS --
184
188 I/O Communications Area Chanm.!1 ID (Locations 168-171): Locations 168-
171, when stored during the execution of a STORE CHANNEL 10 instruction, contain information
which describes the addressed channel. (See STORE CHANNEL 10.) I/O Extended Logout Pointer (Locations 173-
175): The I/O Extended Logout (IOEL) pointer
(locations 173-175) is program-set to designate an
area to be used by channels not capable of storing or
not choosing to store the channel logout information
in the fixed logout area (locations 256-351). The
low-order three bits of the pointer are reserved and
are ignored by the channel so that the I/O extended
logout always begins on a doubleword boundary. Channel logout information may be stored in the 10EL area only when the 10EL mask bit (control
register 14, bit 2) of the CPU to which the channel
is configured is one.
Whether the 10EL facility is used depends on the
channel type and model number. Channels with a
logout length not exceeding 96 bytes use either the 10EL area or locations 256-351 as the logout area.
Channels with a logout length exceeding 96 bytes
use the 10EL area.
Programming Note
The extent of the channel-extended-Iogout area dif­
fers among channels and, for any particular channel,
may depend on the features or engineering changes
installed. In order to provide for such variations, the
program should determine the extent of the logout
by means of STORE CHANNEL 10 whenever a
storage area for the extended logout is to be as­
signed. 240 System/370 Principles of Operation
Limited-Channel Logout (Locations 176-179): The
limited-channel-logout field (locations 176-179)
contains model-independent information related to
equipment errors detected by the channel. This in­
formation is used to provide detailed machine status
when errors have affected I/O operations.
The limited-channel-logout facility may not be
available on all channels. The field, if stored, may
be stored only when the CSW or a portion of the
CSW is stored and mayor may not be accompanied
by the full channel logout. Channels which do not
store the limited-channel-logout field instead usually
store equivalent information in the full channel log­
out.
The bits of the field are defined as follows:
o This bit will always be stored as a zero .when
a limited channel logout (LCL) is stored. If
the program ensures that this bit is set to
one and any channel control check, inter­
face control check, or channel data check
occurs, a test of this bit can determine if the
LCL was stored by the channel. The LCL
cannot be stored by a channel unless one of
these three channel status bits is set.
1-3 Identity of the storage control unit (SC U) through which storage references were di­
rected when an error was detected. This
identity is not necessarily the identity of the
storage unit involved with the transfer.
When only one physical path exists between
channel and storage, the storage control unit
has the identity of the CPU. If more than
one path exists, the storage control unit has
its own identity.
When bit 3 is zero, bits 1 and 2 are mean­
ingless. In this case, the SCU identity is im­
plied to be the same as the CPU identity.
When bit 3 is one, the binary value of bits 1
and 2 identifies a physical SCU. Each SCU in the system has a unique identity.
4-7 Detect field identifies the type of unit that
detected the error. At least one bit is pres­
ent in this field, and mUltiple bits may be set
when more than une unit detects the error.
Bit 4 -- CPU Bit 5 --Channel
Bit 6 --Main-storage control
Bit 7 --Main storage
8-12 Source field indicates the most likely
source of the error. The determination is
made by the channel on the basis of the
type of error check, the location of the
checking station, the information flow path,