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Situations
Contents of'Field
Channel-control check
Status stored by START I/O or
START I/O FAST RELEASE
Status stored by HALT I/O or
HALT DEVICE
Unpredictable
Unchanged
Unchanged
Program check because CCW
location in TIC not provided
Program check (all others)
Disconnected CCW location in
TIC
Address of TIC
+
8
Address of invalid CCW
+
8
Address of TIC
+
8
Disconnected CCW location
First invalid CCW address
+
8
generated
Disconnected data location
Invalid key on CCW fetch
Invalid key on data access
Chaining check
Address of
Address of
Address of
Address of
Address of
Address of
Address of
Address of
invalid CCW
+
8
protected CCW
+
8
current CCW
+
8
last-used CCW
+
8
last-used CCW
+ 8
last-used CCW
+
8
last-used CCW
+
8
last-used CCW
+
8
Termination under count control
Termination by I/O device
Termination by HALT I/O
Termination by CLEAR I/O
Suppression of command
Address of last CCW used in
chaining due to unit check
or unit exception with de-
vice end or control-unit end
the completed operation
+
8
Termination on command
chaining by busy, unit
check, or unit exception
Deferred condition code 1 or 3
Address of CCW specifying
the new operation
+
8
for START I/O FAST RELEASE
PCI flag in CCW
Interface-control check
Channel end after HALT I/O
Address of CCW specifying
the new operation + 8
Address of last-used CCW
+
8
Unpredictable
on selector channel
Channel end after CLEAR I/O
Control-unit end
Device end
Attention
Busy
Status modifier
Contents of the CCW-Address Field in the CSW
Count
Zero
Zero
Zero
Zero
Zero
Zero
Zero
The residual count, in conjunction with the original
count specified in the last CCW used, indicates the
number of bytes transferred to or from the area
designated by the CCW. When an input operation
is concluded, the difference between the original
count in the CCW and the residual count in the
CSW is equal to the number of bytes transferred to
storage; on an output operation, the difference is
equal to the number of bytes transferred to the 1/0
device.
The figure "Contents of the Count Field in the
CSW" lists the contents of the count field for all
situations that can cause the CSW to be stored.
They are listed in the order of priority; that is, if
two situations occur, the CSW appears as for the
situation higher on the list.
Status
The status bits identify the situations that have
been detected during the 110 operation, that have
caused a command to be rejected, or that have
been generated by external events.
When the channel detects several errors, all
corresponding status bits in the CSW may be set to
ones or only one may be set, depending on the
error and model. Errors associated with equipment
malfunctioning have precedence, and whenever
malfunctioning causes an operation to be
terminated, channel-control check,
interface-control check, or channel-data check is
indicated, depending on the error.
When an
operation is concluded by program check,
protection check, or chaining check, the channel
identifies the situation responsible for the
Chapter 12. Input/Output Operations
12-57
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