IBM System/360 2050 User Manual

3. Count specified in the CCW is zero.
4. Data address specified by the CCW exceeds
the storage size.
5. Command address specified by the CCW ex-
ceeds the storage size.
6. CCW sequence in which the first CCW speci-
fied by the command address word is a transfer in
channel.
7. CCW sequence in which two successive CCW' s
specify transfer in channel.
8. Command address specified in the CCW is not
on a doubleword boundary.
9. Command address word in which positions 4-7
are not zero.
The following condition will cause a protection
check:
1. The storage-ptotect tag specified in the com-
mand address word does not agree with the key of
the addressed area of storage during a data store.
The following conditions will cause a chaining
check:
1. The channel accepts more than one byte of
read data assembling on word boundaries when the
CCW specifies byte boundaries on data chaining. This
is detected in the CCW 1 routine.
2. The channel accepts more bytes than CCW
specifies while data chaining. This is detected in
the CCW 2 routine.
Note: Both of the foregoing conditions are caused
by attempting to read data chain with a control unit
whose data rate is faster than the maximum speci-
fied in the Field Engineering Theory of Operation
Manual, Model 50 Functional Units, SY22-2822.
Mode Switch Settings
Stop Mode: The system is not stopped and a master
check does not occur. If the system is not masked,
an I/O interrupt occurs. If error occurred during
an initiation of a new I/O instruction, logout takes
place and a CSW is stored.
Channel Stop Mode: The system is stopped by a log
request in the check register and a master check.
The channel indicators remain unchanged.
Process or Disable Mode: Same as for stop mode.
Data Check
The following conditions will cause a data check:
1. A parity check on 'bus in' while reading data
into the channel. The parity is corrected before the
data is set into the c-register.
2. A parity check is detected on write data going
to 'bus out'. The parity is not corrected.
16 (3/71) Model 50 FEMM
Mode Switch Settings
Process or Disable Mode: Channel proceeds to end
of record; when channel is not masked an I/O inter-
rupt occurs.
Stop or Channel Stop Mode: The channel stops. A
~a~ter c;hec!< an.d log request (CPU roller 2, position
6) are displayed.
SIM Check
This check .indicator informs the channel to terminate
an operation. It indicate$ that control unit status is
not available for the CSW. SIM check occurs only
inside the channel and never appears in the CSW.
The following conditions set SIM check:
1. Channel detects an error before the control
unit can be selected to perform an operation.
2.. A halt I/O instruction terminates the current
operation.
3. An interface selective reset caused by an inter-
face control check occurring.in disable mode.
Incorrect Lengthlndication (ILI)
This indication appears in the CSW and will suppress
command chaining unless the suppress incorrect
length indication (SIL!) flag is present in the current
CSW. If the current CCW has a data chain and a
SIL! flag, the indication is not suppressed and will
appear in the CSW.
The indication cannot occur on a command im-
mediate. When the channel pref etches an invalid CC W
(storage-protect or program check) on a write data
chain operation and the control unit sends status in
before the count in the cu.rrent CCW is exhausted.
the ILi indication will suppress the storage -protect
or program check condition. This is also true if the
channel prefetches data with an invalid data address.
The ILI indication cannot appear in the CSW as a re-
sult of a program controlled interrupt (PCI) flag.
ILi is turned on by the following conditions:
1. A control unit sends service in one or more
times after the count in the CCW has been exhausted.
On a read operation the extra bytes are not placed
in main storage. An extra service in almost always
occurs on a write or control operation. the only ex-
ception being on a formatted type device with a fixed
record length. The residual count in the CSW is
zero.
2. Service in is sent by a control unit less times
than specified by the CCW. The residual count in
the CSW is not zero.

IBM System/360 2050 Specifications

General

Brand	IBM
Model	System/360 2050
Category	Computer Hardware
Language	English