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difference between the checksurr central
wcrd and the contents of control storage.
1.18.4 OPERAToR•s CONTROL PANEL (OCP)
INDICATORS
1.18.4.1 Power On Key
This key is backlighted in white to
indicate that the system power-on sequence
is completed.
If the key glcws r;ink, the
pcwer-on er r:ower-off sequence cannot be
completed because of a rralfunction in a
r:cwer sur:i:;ly or an I/C unit.
1.18.4.2 Pluggable Indicators
Refer tc IBM system/360 Model 25 External
Field Definitions, Form Z29-2176.
1 .• 18. 5 KEYS
Only those keys that have special
significance in the maintenance strategy
are discussed here.
Refer to the Medel 25
FE'IQM. Form Y24-3527 for
a
comr:lete
description of the console keys.
1.18.5.1 control Storage Load
This key is used to initialize the systerr
when:
1.
Operating modes are to be changed (as
frorr Model 25 mode to 1400 mode),
2.
The contents of control storage have
been affected by a systerr failure, er
3.
The system is teing returned to the
customer after extensive service <such
as engineering change activity.)
1.18.5.2 PSW Restart
This key is used to restart an application
using the IPL PSW, rather than the current
PSW used when the system-reset key is
r:re:;sed.
1.1§.5.3 Control Address Set
This key must te pressed to allow the CE to
restart the microprogram at an address
ether than that specified ty the normal
control-storage addressing rreans.
The CTRL
ADR SET key is op er at ional only when the
CPU clock is off.
1.1S .• 5.4 Enable Control Storage Store
This switch must te pressed and held during
a store into the control storage area of
core storage so that the control-storage
store circuitry rena.ins activated.
The
storage or:eration is successful when the
new information is displayed in the byte-0
and byte-1 indicators.
1-124
(7/69)
This key is effective cnly when the
use-meter key switch is in the CE position.
1.18. 5. 5 Printer-Keyboard Alter/Display
Although this key is available for customer
use, it is used in maintenance strategy to
control certain phases en the 1052
diagnostics.
1.18.6 Y.CDE SWI'ICH
Only switch positions that are unique to
the Y.odel 25 maintenance strategy are
described here.
Refer tc the Model 25
FETOM, Form Y24-3527 for complete
information.
1.18.6.1 Y.ain Storage Address Stof
With the switch in MS ADR STOP position,
the machine stops at the completion of the
microword in progress when the address in
switches A, B, C, and D rratches the address
of the core-storage location being
accessed.
The address-rratch indicator
turns on.
Byte-0 and byte-1 indicators
display the address of the position of
memory that was just accessed.
The match
occurs for addresses that specify either
program or control storage.
1.18.7 DIAGNOSTIC CONI'ROL SWITCH
1 .18 • 7 .1 Stop
When the switch is in this position and no
hubs are wired on the CE back panel, the
system stops every cycle.
When a circuitry
line is wired to the COND IN hub on the CE
back panel, the system steps every cycle in
which the line goes positive.
1.
.18.
7. 2
'Ira12
This position forces a trap to the CE trap
area of control storage.
With the
diagnostic control switch in the trap
position and either (1) no wiring to the CE
panel.
or (2) a positive pulse to the IN
hub of the CE panel, the rrachine-check
latch is set and a trap is taken to 0280.
If priority is not established in the trap
routine, the trap to 0280 is repeated every
other cycle.
'Ihe CE trap routine can be
used to log inforrration en the
printer-keyboard.
1.18.7.3 scan storage
With the switch in this position, all core
storage positions are read and regenerated.
When the check control switch is in the
stop position, a farity error on storage
data or a storage address causes a hard
stop.
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