at
its
normal
rate
(e.
g.,
fixed
duration
control
sequences
may
not
take
effect
and
diagnostic
control commands
which
operate
upon BP's registers or memory
locations
require
a
large
number
of
clock
steps to
complete
the
operation).
The
RESET
SYSTEM,
RESET
I/o,
and
RESET
BASIC
PROCESSOR commands
are
effective
in Single
Clock
Mode.
When
the
SingleClock
Mode is
set,
the
contents
of
the
currently
selected
Single
Clock
Status
Register
are
displayed
(see SELECT/DISPLAY
SINGLE CLOCK
STATUS
REGISTER,
ZCE## command).
If
the
computer
system is
currently
in
the
Single
Clock
Mode,
ZCCLK
command
resets
the
two-digit
clock
step
counter
to
X'OO'.
The
Single
Clock
Mode may be
reset
by
either
a
CLEAR
SINGLE CLOCK MODE, ZCKIL, command or a
SUPER
RESET,
Z
C
MM4, command.
Note:
Entering a
SET
SINGLE CLOCK MODE command
when
the
basic
processor
is
performing normal
data
pro-
cessing
operations
may
have
an
adverse
effect
upon
I/O
operations.
To
prevent
inadvertent
entry
into
Single
Clock
Mode,
the
ZCCLK command is not
ac-
cepted
unless
the
MAINT MODE switch is in
the
ON
position. Attempting
to
enter
a ZCCLK command
when
the
MAINT MODE switch is in
the
OFF
posi-
tion
results in
an
error
message (*EVENT A2*)
being
displayed
and
no further
action.
)I SINGLE-CLOCK
STEP
When
the
system is in
the
Single
Clock
Mode,
a
single
space
character
(depicted
as
~
within
this
text),
without
a
control-Z,
is·
interpreted
as a SINGLE-CLOCK
STEP
command. For
each
space
character
received
from
the
con-
trol
console,
the
current
command or
instruction
is
partially
executed
(one
clock's
worth
of
execution
for
each
space
character)
•
The
contents
of
the
currently
selected
Single
Clock
Status
Register
are
displayed
and
the
dock
step
counter
is
incre-
mented by + 1 for
each
SINGLE-CLOCK
STEP.
zCC##
MULTIPLE-CLOCK
STEP
When
thesystemisintheSingle
Clock
Mode,
the
MULTIPLE-
CLOCK
STEP
command
causes
the
current
instruction
or
com-
mand
to
be
executed
for 1
to
256
clock
steps (as
specified
by
the
two
hexadecimal
digits
"##"
in this command). The
ZCOO
command
causes
256
clocks
to
be
issued. The
contents
of
the
currently
selected
Single
Clock
Status Register
are
displayed.
The
clock
step
counter
is
incremented
by
the
number of
clock
steps
specified
by this command.
The
MULTIPLE-CLOCK
STEP
command
allows
precise
step-
ping
to
a
specific
point
in a micro-program
sequence
in-
volving
a
large
number of
clock
steps.
142
Control Commands
SELECT/DISPLAY
SINGLE CLOCK
STATUS
REGISTER
This command
causes
the
requested
SCSR
to
be
displayed.
The
n##n
portion
of
this
command (two
hexadecimal
digits)
is stored
within
the
ECS
and used
as
a
reference
address in
any command which displays
the
contents
of
the
currently
selected
Single
Clock
Status Register. The first
hexa-
decimal
digit
is
the
cluster
address
and
the
second
digit
is
the
element
address.
In
addition
to
being
modified by subsequent
Zc
E
##
com-
mands,
the
cluster
and
element
addresses may
also
be
changed
by
the
LOAD NORMAL command and
the
SET
CLUSTER
DISPLAY
MODE command. The LOAD NORMAL
command sets
the
address
to
X'OO'
and
the
SET
CLUSTER
DISPLAY MODE command causes
the
element
address
to
be
set
to
a
zero
following
each
cluster
scan.
Zct<IL
CLEAR
SINGLE CLOCK MODE
When this command is
entered,
the
system
clocks
are
re-
started
immediately.
The
ZCKIL
command may
be
issued
at
any
time.
If
the
system is not in
the
Single
Clock
Mode,
the
ZCKIL command is ignored.
Zc:r..MO
CLEAR
MM
FEATURES
Upon
completion
of
maintenance
operations,
the
CLEAR
MM
FEATURES
command (as well as
the
SUPER
RESET
com-
mand,
described
below) may
be
used
to
restore
the
system
to
a standard
configuration
status. The
CLEAR
MM
FEATURES
command
does
the
following:
1. Restores
the
system
clock
to
its normal
frequency.
2.
Clears
the
"Repeat
Clocking
Mode" (see
ZC
MM1
command).
3.
Clears
the
"Cluster
Display Mode" (see
ZC
MM2
command).
4.
c
Clears
the"
P-Mode
Repeat Mode" (see Z MM3
command).
5.
Clears
the"
Micro-diagnostic
Repeat Mode" (see
ZC
MM5 command).
6.
Clears
the"
Override
Interleave
Mode" (see
ZC
MM9
command).
7.
Clears
the"
Display
Inhibit
Mode" (see
ZC
MMA
command).
Note
that
the
CLEAR
MM
FEATURES
command does not
generate
any
resets (ZCRIO, ZCRSY, or
ZCRBP),
does not
clear
P-Mode,
nor does
it
clear
Single
Clock
Mode (see
ZCCLK
and
ZCKIL commands).
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