Xerox 560 Reference Manual page 165

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
numberof 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·Single Clock
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 acti on.
16
SINGLE-CLOCK STEP
" , I .1 • . . . 1 ~. I I ll. I • I
YVrll::lI rill:: :)y!)rl::lII I!) III HII::
.J"I~II::
\..IOCK. IYlOUl::, U
!)"~II::
space character (depicted as
!t5
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 c1ock ' s worth of execution for each space
character) .
The contents of the currently selected Single Clock Status
Register are displayed and the clock 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 11## .. 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.
SELECT/DISPLAY SINGLE CLOCK STATUS
REGISTER
This command causes the requested SCSR to be displayed.
The Ir##lr 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 el ement 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 XIOO' 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.
z'\1MO
CLEAR MM FEATURES
Upon completion of maintenance operations, the CLEAR
1.1~A
....... T'lln .. t'" __ .
_ •• 1 / .
.11 . . • .
1..
t'"llnl':'n nl':'t'"["'T' . . .
IYIIYI rLMI UI'l.L.J \,;UlIIIIIUIIU \U!) VVI::II U!) 1111:: .JU"- LI'I. I'I.L.JL I \';UlII-
mand, described below) may be used to restore the system
to a standard configurati on 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
II
P-Mode Repeat Mode" (see Z MM3
command).
5. Clears the
II
Micro-diagnostic Repeat Mode" (see
Z
C
MM5 command).
6. C
I
ears the
II
Overri de Interl eave Mode" (see ZC MM9
command).
7. Clears the
II
Display Inhibit Modell (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).
Control Commands 159