TM 1–1520–238–T–3
Change 5
1–3
Section II. MULTIPLEX READ CODE INTERPRETATIONS
NOTE
Multiplex read codes are observed on the HOD (ADC) or
CDU (ADD).
1–6 FAILURE SYMPTOM PARAGRAPH.
Multiplex read codes are interpreted through the use of failure symptom paragraphs. (See Example.) Failure
symptom paragraphs provide information which can be used in locating failures with multiplex read codes during a
Maintenance Operational Check (MOC). Failure symptom paragraphs specify a known or expected aircraft MOC
CONDITION and the corresponding SIGNAL NAME, MEMORY LOCATION to be examined and MEMORY DATA
BITS being examined in the MEMORY LOCATION. Comparing the aircraft CONDITION with the displayed multiplex
read code response allows fault isolation through the use of information presented under SIGNAL FUNCTIONS,
REMARKS, PASS and FAIL.
EXAMPLE:
17–2 SIGNAL NAME: DEK SWITCH
MEMORY LOCATION: 000444
MEMORY DATA BIT(S): 8–11 (HEX)
CONDITION: If fourth digit displayed on HOD is 0=STBY.
If fourth digit displayed on HOD is 1=RANGE.
If fourth digit displayed on HOD is 2=FD/LS.
If fourth digit displayed on HOD is 3=(NOT USED).
If fourth digit displayed on HOD is 4=TGT.
If fourth digit displayed on HOD is 5=CODE.
If fourth digit displayed on HOD is 6=SP1.
If fourth digit displayed on HOD is 7=OFF.
SIGNAL FUNCTION: Monitors position of DEK DATA ENTRY switch.
REMARKS: From DEK through CPG MRTU Type III to FCC. Selects operating mode for
fire control system.
PASS: If CONDITION corresponds to proper mode for switch selected, go to paragraph
17–3.
FAIL: Location of fault: DEK, wiring from DEK to CPG MRTU Type III, CPG MRTU Type
III. Troubleshoot wiring to isolate fault TM 9–1230–476–20–2.
1–7 SIGNAL NAME.
The SIGNAL NAME is the common or abbreviated name for an input or output.
EXAMPLE:
17–22 SIGNAL NAME: DEK SWITCH
Abbreviations and acronyms can be found in the List of Abbreviations located in the Glossary.
1–8 MEMORY LOCATION.
The MEMORY LOCATION is the octal address of the signal name data you are going to inspect.
EXAMPLE:
MEMORY LOCATION: 000444
1–9 MEMORY DATA BITS.
a.
Memory data indicates the bit(s) to be examined in a 16-bit word. These bits are used by the fire control
computer (FCC) to determine the status of system/Line Replaceable Units (LRU). The numbers to the right of the
memory location on the HOD are memory data octal representations. Multiplex read code responses are read
from right to left. See Figure 1–1 (ADC) and Figure 1–1.1 (ADD).
