PROCESSING OF ASYNCHRONOUS INPUTS-CONT.

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3011

sequence, issues a stuff command to the common

two modes: transition encoder or timing recovery. Both

electronics gated clock generator. In response to the

modes provide the incoming data stream with an

stuff command, the gated clock generator appropriately

associated timing signal. with timing thus supplied, the

adjusts the number of gated clocks sent to the channel's

TE/TR card then uses the previously discussed rate

output counter during a predetermined interval. The

buffering, asynchronous-to-synchronous conversion

adjustment causes the output counter again to become

process to supply the multiplexer common electronics

offset from the input counter by the established nominal

section with synchronous digital data.

value. For example, if the output counter is determined

to be operating slower than the input counter, a gated

5-39. In the TE mode, sense transitions (low to high or

clock is added. Conversely, a gated clock is deleted

high to low) occurring in the input data stream are

when it is necessary to slow the counter. The overall

detected and encoded for subsequent processing. Under

process of gated clock addition/deletion, the sequence in

control of an independently generated multiplexer timing

which the operation is performed, and the process by

signal, each detected transition is encoded into a 3-bit

which the operation is reversed at the demultiplexer

data word. The timing signal, which occurs at a rate at

output is termed overhead servicing. The overhead

least three times that of the nominal input data bit rate,

service function is described in paragraph 5-48.

also clocks the input counter of the rate buffering portion

of the TE/TR card. As previously discussed, the output

5-37.

The basic input rate buffering, asynchronous-to-

of the rate buffering function is synchronous with other

synchronous conversion process discussed above is

timing signals in the multiplexer common electronics

performed by the RCB card, and is applicable to

section.

multiplexer channels being inputted with digital data and

associated timing. While most channel inputs are in this

5-40. In the TR mode, the TE/TR card accepts a data

form, voice and digital data without associated timing are

input without associated timing and provides a timing

also accepted as channel inputs by the multiplexer.

signal for use in the subsequent rate buffering operation.

Voice inputs are processed by a VE card. The VE card

Timing provided by the TR function is derived from an

performs analog-to-digital conversion of the voice signal

independent high frequency clock generator on the

and provides the common electronics section with a

TE/TR card. Divided to the nominal bit rate of the

digitally encoded representation of the voice input. The

channel's input data stream, the timing is automatically

timing used in the encoding process is the gated clock

phase adjusted to coincide with data transitions

signal. Since the gated clock signal is derived from and

occurring at this rate.

The input data stream,

is therefore synchronous with the multiplexer reference

accompanied by its recovered timing, is then routed to

timing source, the output of the VE card is in the required

the rate buffering function on the card, leaving the card in

synchronous digital form.

a digital form that is synchronous with the timing signals

in the multiplexer's common electronics section.

5-38. Digital data inputs applied to the multiplexer

without associated timing are processed by the TE/TR

5-41. As described in paragraphs 5-31 through 5-40,

channel card. The TE/TR card operates in one of

four methods can be used

5-10