TRANSITION ENCODER/TIMING RECOVERY (TE/TR) CARD

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3011

ppm of the incoming data rate, a channel sampling rate

precision multiplexer channel sampling rate (KRp)

that is higher than the incoming data rate is selected. In

applied to the channel. During word 24, the rate

this configuration, the RCB/URC switch on the card is set

comparison function is initiated by word 24 bit 0 signal

to the URC position to place the coarse rate conversion

MW2401 from the OEG card. At this time, the rate

circuits in series with the applied gated clocks. The

compare circuits effectively subtract the count in the

coarse rate conversion circuits are configured to delete a

write address from the count in the read address. In

predetermined number of gated clock signals and

normal operation, there is a predetermined difference

effectively lower the channel sampling rate to within +250

count between the two addresses. When the difference

ppm of the incoming data rate. The word 24 signal

count from a rate compare is the predetermined figure, a

MW24N1, end-of-scan signal MEOS3NX, and minor

no action request is generated. When the incoming bit

frame terminal count signal MMFC31 are timing signals

rate increases, the difference count indicates that the

that control the selection of the individual gated clock

write address is greater than the read address. At this

pulses that are deleted, inhibit the coarse rate conversion

time, a positive stuff request is generated and applied to

circuits during word 29 when overhead servicing is

the OEG card. As a result, an additional gated clock

performed, and preset the circuits after each major

pulse applied to the RCB card effectively helps the read

frame period. The coarse rate conversion circuits are

address counter to catch up. When the difference count

independent of the positive and negative stuff function

indicates that the incoming bit rate has decreased, the

performed in the rate conversion buffer circuits as

write address is less than the read address and a

described in paragraph 5-74. Fixed amounts of gated

negative stuff request is generated. The result is that one

clock pulses are deleted by the coarse rate conversion

normal gated clock pulse to the RCB card is deleted,

circuits during each major frame period.

which effectively slows down the channel sampling rate

of the read address counter. The stuffing action for

5-76. TRANSITION ENCODER/TIMING RECOVERY

either the positive or negative stuff condition continues

(TE/TR) CARD.

as long as the rate compare circuits determine that the

incoming bit rate and the channel sampling rate are not

5-77

The TE/TR card processes digital data that are

nominally the same. Each used port assigned to a given

applied to the multiplexer without timing. The circuits on

channel is eligible to receive overhead servicing during

the card are divided into three functional circuits: the

one minor frame in each minor frame period.

transition encoder circuits that receive and process

digital data whose bit rate is 400 bps or less; the timing

5-75. Initially, when an RCB card is configured for a

recovery circuits that receive and process digital data

data channel and the applied data rate to the card is the

whose bit rate is 75, 100, 150, 300, 600, 1200, 4800, or

same (within +250 ppm) as the channel sampling rate

applied to the card, the RCB/URC switch on the card is

9600 bps; and the rate comparison buffer (RCB) circuits

set to the RCB position. With the switch in the RCB

that receive the data from the transition encoder or the

position, the circuits on the card function as described

timing recovery circuits and resynchronize the data bits

above. When the channel sampling rate for a channel

with the multiplexer timing as described in the RCB card

not

configured

within

+250

discussion.

Change 1 5-21