Diagnostic Control Commands - Xerox 560 Reference Manual

and the IDLE indicator is illuminated. In the IDLE state
the load commands, the reset commands, and the RUN com-
mand are enabled. The I/O system may continue to perform
I/o operations initiated prior to the ZCHLT command, even
though the BP is halted. Note that the processor HALT
status is not set by the ZCHLT command, but is caused by
internal processor conditions (see
II
Processor-Control Word").
SYSTEM RUN
The RUN command is accepted only if the BP is in the
IDLE state. When the FUN command is accepted, the BP
is allowed to execute its instruction stream. On the SCP,
the IDLE indicator is extinguished and the RUN indicator
is illuminated, subject to the processor control word and
system status.
When not in the IDLE state, the system does not accept any
of the load and reset control commands. Attempti ng to enter
any load and reset control command while the system is in
the RUN mode results in an error message being displayed
on the control console (see Table F- ).
DIAGNOSTIC CONTROL COMMANDS
Diagnostic control commands facilitate isolating software
and hardware problems by providing single-instruction ex-
ecution, as well as permitting read/write access to many
processor internal control registers and system memory loc-
ations. To perform diagnostic commands, BP instruction
execution must be interrupted and the ECS control mode
altered. This is accomplished by the ENTER P-MODE com-
mand (a "CONTROL-P" character generated by depressing
CONTROL and P keys simultaneously). Once in P-Mode
the system is forced into the IDLE state and the BP stores
and fetches data or executes single instructions only upon
request from the operator through the SCC.
Note: Within this text the control-P character is repre-
- - sented by the following symbol, pc.
The diagnostic control (P-Mode) command format differs
from the basic command format. Hexadecimal digits are
immediately echoed and stored to be used as data or ad-
dress depending on the following command. The system
truncates the data stream to eight hexadecimal digits and
assumes leading zeros if less than eight characters are en-
tered. All non-hexadecimal characters, except basic (ZC)
format commands, are treated as P-Mode commands. If the
character is not in the allowed commond set; it is echoed
followed by a question mark
II
N?" and no action results.
Valid commands are echoed; the requested operation is
then performed and a P-Mode data display of the form
II
P:DDDDDDDD @ AAAAAAAN' is generated on the next
line of SCC pri ntout. The
II
pil represents the processor ad-
dress (normally 0); the
II
D" field (eight hexadecimal digits)
156 Control Commands
represents the data in the location specified in the
II
A"
field (eight hexadecimal digits). The first hexadecimal
digit of the A field is XIOI for memory addresses and X ' 8 1
for internal register addresses. All valid commands, except
EXIT P-MODE, produce a display in this format.
The allowed diagnostic command set is listed in Table 22.
An example of the resulting printout is shown in the section
entitled ,rOperating Procedures and Information".
pC ENTER P-MODE
The ENTER P-MODE control command is generated by de-
pressing the CONTROL and P keys, simultaneously (pc).
The system is forced into the IDLE state and the processor
wi II execute diagnostic control commands entered from the
System Control Console. The ECS remains in the P-Mode
until an EXIT P-MODE command (described below) is
entered or the ZC format commands SYSTEM RUN or LOAD
NORMAL are entered. Successful entry into the P-Mode
is indicated by a P-Mode display on the SCC.
(P-Mode)
SELECT INTERNAL REGISTER ADDRESSING
(P-Mode)
/ SELECT MEMORY ADDRESSING
These commands specify the storage element whose con-
tents are to be displayed and operated upon with subsequent
commands. The "/" character following a hexadecimal
data stream specifies a memory address; the ".
II
character
specifies an internal processor control register address. All
address calculations and memory accesses are subject to
the write lock keys, address mode, and mapping bits in the
program status words.
(P-Mode)
+
ADD TO SELECTED LOCATION
The
"+"
character, following a hexadecimal data stream,
causes the value of the data to be added to the contents of
the selected storage element.
(P-Mode)
SUBTRACT FROM SELECTED LOCATION
The "_" character, followi ng a hexadecimal data stream,
causes the value of the data to be subtracted from the
contents of the selected storage element.
(P-Mode)
M
STORE IN SELECTED LOCATION
The
II
Mil character, following a hexadecimal data stream,
causes the data to be stored in the selected storage element.