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routines. and unused control-stcrage
lccations.
1.17.4 CPU ATTACHMEN'I CHECKS
This section describes sorre cafabilities
for handling check conditions occurring
within th€ integrated I/C attachrrent
devices.
For furtb€r information, consult
the index in this manual for the Sfecific
area of interest.
1.17.4.1 2540 Attachment Checks
1.
Overrun--This check occurs when all ten
traps that must te completed during
each row have not occurred by the tirre
the next row is ready to be read.
Priority circuitry ensures that overrun
will not occur unless there is a
hardware failure.
2.
Sync Check--This check ensures that the
shift registers receiving data from the
1540 are in synchronisrr with each
ct.
her.
3.
Address Check--This check is en the
address sent to the 2540 for each bit.
It checks for a 2/5 code, and for an
address greater than or equal to 90.
Each of these checks will give a unit
check to the status byte, with equipment
check in the sense informaticn.
Hardware
checks in the 2540 unit will give the sane
status and sense information to the program
as the 2821.
The rricroprogram interrogates
the attachment hardware checks; the 2540
unit checks combines this with the
informaticn it may detect itself and places
the result in the proper sense bi ts.
The
rricroprcgram forms the status and sense
informaticn.
1.17 .• 4. 2 1403 Attachment Checks
1.
Hammer Check--Equiprrent check sense
bit.
This check is made to determine
if each harrmer driver that was
requested to operate. did operate.
2.
Sync Check--Intervention-required sense
bit.
This check indicates that the
chain or train and the printer controls
are out of synchronisrr.
3.
p"rint BUffer Parity Check--Equipment
check sense bit.
This check is for
correct parity on data read from the
print buffer while printing a line or
when receiving data frorr the CPU.
The 1403 microprograII1 inte'rrcgates the
hardware check information and sets the
proper sense and status inf ormaticn.
The
rricroprogram also checks information for
printability when loading the buffer. and
signals data check for unprintable
characters.
This depends on the
information loaded at CSL tirre into the
module of auxiliary storage used as the
print translator, or loaded by the UCS
utility pro.gram UT048.
The 1052 (PR-KB)
printouts of the printer area of auxiliary
storage are shown in Section 1.14.
1.17.4.3 1052 Attachroent Checks
The 1052 hardware checks the keyboard data
for proper parity.
The rricroprogram
detection of a parity error would cause
unit-check status and the equipment check
sense l::it to te set.
1.17.4.4 2311 Attachment Checks
1.
Data check--unit-check status--data
check sense.
This check occurs when
data read frorr the file does not
generate the proper check character.
2.
Overrun--unit-check status--overrun
sense.
This check occurs when the
attachment requires service from the
CPU and does not receive it soon enough
to keep from losing data or causing
improper operation.
The 2311 attachment rricrcprogram checks
the hardware signals from the 2311 for
errors detected in the unit, interrogates
the attachment checks and sets the
appropriate status and sense information.
1.17.4.5 Channel Checks
1.
Incorrect Length Check--occurs when the
number of bytes contained in the
storage areas assigned for the I/O
operation is not equal to the number
of
bytes requested or offered by the I/O
device.
2.
Program Check--occurs when programming
errors are detected by the channel.
3.
Protection Check--occurs when the
channel atteII1pts to place data in a
portion of rrain storage that is
protected for the current operation on
the subchannel ; or, the protection key
associated with the I/O Oferation does
not match the key of the addressed
main-storage locaticn, and the
protection key is not zero.
4.
Channel Data check--indicates that the
channel has detected a parity error in
the inf orrraticn transferred to or from
main storage during an I/O operation.
5.
Channel Control Check--caused by any
nachine rralfunction affecting channel
controls.
This includes parity errors
on ccw and data addresses and parity
errors on the cont en ts of the ccw.
(Logout is initiated.>
6.
Interface Control Check--caused by an
invalid signal on the I/O interface.
The condition is detected by the
channel and usually indicates
nalfunctioning of an I/O device.
(Logout is initiated.)
2025 FEMM (7/69)
1-117
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