PARALLEL FORMAT.-- In this format, the data
Testing of memory functions
transmitting and receiving electronics hardware must
Testing of the central processing unit (CPU)
have one data line (wire) for each data bit. For example,
a 10-bit data word requires 10 data lines. In parallel data
Testing of the input/output (I/O) channels
word transmission and reception, each bit of the data
VERIFICATION OF MEMORY CONTENTS.--
word is presented simultaneously on the data lines.
When the ECU program is loaded into the ECU, a
Therefore, the entire data word is sent or received
specific memory location contains the arithmetic sum
simultaneously. Parallel format is used only for data
of all "fixed" memory locations; that is, the arithmetic
communication within a console to allow a more rapid
sum of the contents of all memory locations that cannot
communication and transfer of information. This format
be changed during operation. When the program is
a l s o reduces the amount of electronic hardware
restarted, the computer will automatically add the
required.
location contents and compare the two sums. If the two
SERIAL FORMAT.-- In the serial format, data bits
sums do not agree, the computer will halt or "lock up."
are sent and received one at a time in a timed sequential
TESTING OF MEMORY FUNCTIONS.-- Again,
manner using a single data line. Serial format is used for
when the ECU program is loaded, a series of test pat-
data communication within a console and between
terns are assigned to specific memory locations. These
consoles. The data line between consoles is time shared,
test patterns are used to store and retrieve information
and clock synchronization between the consoles permits
from any memory location that can be changed during
information exchange control. There are three types of
operation. The test pattern is stored, retrieved, and
data lines for serial data transmission. They are called
finally compared to the original test pattern. If the two
subsystems and are as follows:
patterns do not agree, the ECU will halt.
Command and control serial data subsystem
TESTING THE CPU.-- Upon progam start-up or
Demand display serial data subsystem
as a rest mode background test, all commands for the
CPU are tested. All possible combinations of data
Digitized analog serial data subsystem
needed to execute the program are also tested.
The advantage of the serial data format is the significant
TESTING THE I/O CHANNELS.-- This test
r e d u c t i o n of the amount of wiring required for
verifies the operation of the interface functions. This is
accomplished by sending a test pattern out into the
system and then receiving it back from the system. A
TESTING AND CALIBRATION METHODS
comparison determines proper operation. Again, the
computer will halt should the comparison fail.
In this section, we will briefly discuss the methods
used by the ECSS and the GSEs to test and calibrate the
If the computer halts because of a test failure, it will
engineering control system used on DD-963, DDG-993,
identify the nature of the failure by the data display light
and CG-47 class ships. We will discuss the tests
emitting diodes (LEDs) on the ECU. To determine the
automatically performed by the executive control unit
failure, the repair GSE selects the CPU position on the
(ECU). We will also briefly discuss the calibration
DISPLAY SELECT switch. The LEDs 0 through 4 will
procedures that you, the repair GSE, should use. For a
indicate the location of the failure.
more detailed description of the tests required to
maintain ECSS equipment, refer to the appropriate
Calibration Process
technical manuals.
A calibration subprogram contains a listing of all the
ECU Self-Tests
tables you will need to set the calibrated values into the
S/CEs. The information contained in these tables
The ECU program tests the functions of the ECU as
includes voltage equivalents for power turbine
a rest mode background test. That is, the self-test
overspeed trip set points, gas generator speed range, and
routines are done when the program is restarted or when
header pressure transducer inputs.
commanded by actuation of the required program sense
To start the calibration process, you will energize
switches on the ECU control panel. The self-tests are
the calibration panel in one of the S/CEs and select the
broken down into four groups.
type of card to be calibrated. Once you place the card in
Verification of memory contents
the calibration slot, the computer will identify the
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