Diagnostic Function - TM-11-5805-688-14-10173

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3010

22 are required to obtain the reverse binary numbers for

5-284. Each active port has access to overhead service

ports 3, 19, 11, 7, and 15. For example, the binary count

one time in each major frame period during a selected

for 25 in reverse is port 19. Also, in the forward binary

minor frame. The port assignment for a given minor

code listing, binary numbers for 7, 11, 15, 19, 23, 27 and

frame is controlled by the minor frame equals port

29 are deleted, since their reverse binary numbers are

sequence comparator. The comparator generates an

greater than 22. For example, binary count 7 in reverse

A=B output signal when the read port address from the

is port 28. Therefore, to add and delete the necessary

read port address counter matches the minor frame

forward binary numbers, the circuit function described in

count (MMFCO through MMFC4). An A=B output signal

paragraph 5-293 is required.

is generated once each scan, but is generated through

AND gate U47B as signal MMF=PS during word 28. At

5-283. The following circuits perform the addition and

the time that MMF=PS is generated, the port receiving

deletion function necessary to develop an address for

the overhead service is the reverse binary equivalent of

each of the active ports in the system. The 5-bit read

the binary output from the read port address counter.

port address from the read port address counter is

Since the port selected is the reverse binary equivalent

applied to an N+1l adder that increases the binary count

of the counter output, each active channel receives the

by one. The weights of the 4-bit binary code output from

near-homogeneous overhead service at its associated

the adder are reversed so that the address applied to the

ports.

read ports-in-use comparator is the same as the read

port address being applied to the R.A.M. plus one. The

5-285. Diagnostic Function.

reversed binary address is compared against the ports-

in-use binary count that represents the maximum

5-286. The diagnostic circuits on the sequencer card

number of active ports in the system. When the

perform two functions. The main function is to provide

reversed read port address is a binary number that

an error indication when a hardware malfunction occurs.

exceeds the maximum number of active ports, an A is

Two diagnostic signals can be generated from the

greater than B output from the comparator enables the

diagnostic circuits: loss of end of scan signal MLEOS-,

read reset generator. The read reset generator, in turn,

which is generated when a loss of the end-of-scan signal

produces a preset signal that presets the read port

is detected; and sequencer diagnostic signal MSEQ-,

address counter to its present count plus two. Thus, the

which is generated when a hardware malfunction

counter skips the undesired read port address and

affecting the channel address sequence is detected.

proceeds to the next count, which is an active port.

The second function of the circuits is to initiate a R.A.M.

Thus, the read port counter produces an equal number

rewrite condition when a channel address check detects

of read port addresses that equals the number of active

an out-of-sequence condition.

ports. Table 5-4 shows the truncated listing for a 22

used ports system.

5-287. The end-of-scan activity detector generates an

error signal when signal MEOS2 from the end-of-scan

gate U47A and to the loss-of-scan diagnostic latch. The

5-72