System!370
Model
168 (cont'd)
To
Alter (Store into) Main Storage
Every store operation should be preceded
by
a display operation to prevent destruction
of
data by doubleword storing. For real addresses, use "Display
Main
Storage" pro-
cedure; for logical addresses, use "Translate Address and Display
Main
Storage" pro-
cedure shown after this procedure.
1.
Perform steps 1 through 7 of "Display
Main
Storage" or "Translate Address
and Display
Main
Storage."
2. Set MANUAL ENTRY SELECT
to
MCDR.
3. Press cursor advance key
=>
until the cursor underscores the byte
in
MCDR
where the data
is
to
be
entered.
4. Enter
the
data change by pressing
the
data keys.
As
soon
as
the byte
is
entered
in
the MCER, it
is
transferred to the
MCDR
where it can be check·
ed for accuracy.
If
an
error occurs, press the cursor advance key until
wraparound occurs, and return to
the
byte desired. Enter the correct data.
Translate Address and Display
Main
Storage
The CRT displays eight bytes, starting with the
logical location addressed.
1.
Press STOP. Manual light turns on.
2.
Set CRT
MODE
SELECT to
CEo
3. Set STORAGE SELECT
to
MAIN
STOR.
4.
Set
MANUAL ENTRY SELECT
to
MCAR
to
enter the logical (virtual)
address.
5. Press the cursor advance
k~y
=>
until the cursor underscores the second
byte
in
MCAR. (The first byte
is
ignored.)
6. Enter a six-hex-digit logical address by pressing the data keys.
As
each key
is
pressed,
the
appropriate digit appears
in
the MCER.
As
every second digit
completes a byte,
that
byte appears
in
the
MCAR
and the cursor advances
to
the
next byte.
7. Press TSLT ADR & DISPLAY MAIN. The
real
address replaces the logical
address
in
MCAR,
and the data at
the
real address appears
in
MCDR.
If
Zeros
appear
in
ooth
th~
MCAR
and
MCDR,
t:'ilhel
r.i
ban:;ldliofi
t:}('l:eJ-lliulI
associated with the specified logical address has occurred, or the resulting real
address
is
invalid for the system.
8.
Restore CRT
MODE
SELECT
to
OP.
9. Press START
to
resume processing.
To Stop on Main Storage Address
1.
Press STOP. Manual light turns on.
2.
Set STORAGE SELECT
to
MAIN
STOR.
3. Set ADDRESS COMPARE/SYNC:
to
IC
for a match between the
IC
and the
logical address set
in
the MRAR; or
to
CHAN for a match between a
real
address set
in
the
MRAR
and a main
storage address selected by a channel; or
to
CPU/CHAN for a match between a real address set
in
the
MRAR
and an
address selected either by the
CPU
or by
the
channels;
or
to
CPU
(REAL) for a match between the address selected by
the
CPU
and
the
real address set
in
the MRAR;
or
to
CPU
(LOGICAL) which
is
the same
as
"Real Address" except
that
3
logical address must be entered
in
the MRAR.
4. Set
CS/MS to
MS;
set
stop
on oompare
(MS)
to
STOP.
5. Set CRT
MODE
SELECT
to
CEo
6.
Set MANUAL ENTRY SELECT
to
MRAR.
7. Press cursor advance key
=>
until the cursor underscores the second byte
in
MRAR displayed on the CRT. (Using a six-byte address, ignore
the
first
MRAR byte.)
8. Enter six-hex-digit logical address (where stop
is
desired) by pressing
the
data
keys.
As
each key
is
pressed,
the
appropriate digit appears
in
the
MCE
R.
As
f?,/ery
second digit completes a byte,
that
byte appears
in
the
MRAR
and the
cursor advances
to
the next byte.
If
an error occurs, press the cursor advance
key until wraparound occurs, and return
to
tpe byte desired, then enter [he
correct digits.
9.
Return CRT
MODE
SELECT
to
OP.
10. Press START
to
resume processing.
11. When
the
CPU
stops at the desired compare stop, reset CS/MS
to
CS/MS,
reset stop
on
compare
(MS)
to
NORM, and press START
to
resume pro-
cessing.
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