OVERHEAD SERVICE FUNCTION.

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3011

Reversed

Resultant

Used

Associated

Decimal

Binary

Decimal

Port

Channel

Count

Sequence

Count

00001

10000

Bypass

00010

01000

00011

11000

Bypass

00100

00101

10100

Bypass

00110

01100

weighting to achieve near-homogeneous gating

OEG card. In turn, each channel card responds with one

simplifies the logic implementation required for extracting

of three requests back to the OEG card: no action,

data from the channel cards. This is further described in

positive stuff, or negative stuff. In this discussion,

the theory of operation for the sequencer card

assume that channel card No. 1 requests no action,

(paragraph 5-265).

channel card No. 2 requests a positive stuff, and

channel card No. 3 requests a negative stuff

5-48.

OVERHEAD SERVICE FUNCTION.

5-51. A no-action request from channel card No. 1

5-49. It is possible that the applied channel data rate

indicates that the rate at which data are being written into

could vary with respect to the multiplexer timing rate

the channel card is the same as the rate at which data

since the incoming data are asynchronous to the

are being read out. When the GC/DM gated clock

multiplexer set.

As described in paragraphs 5-30

generator card transmits channel No. 1 address to the

through 5-35, the multiplexer channel cards can detect

OEG card, the no-action request signal is applied back to

differences in the input and output rates and cause

the GC/DM card. As a result, the gated clock generator

corrective action when the differences are less than +250

continues to apply normal gated clock signals GCO1 to

ppm. The differences between the input and output data

channel card No. 1.

bit rates are compensated by the use of an overhead

service function. Using overhead servicing, the multiplex

5-52. A positive stuff request from channel No. 2

function has the ability to add or delete gated clock

indicates that the rate at which data are being written into

signals sent to the channel card as necessary to

the channel card is greater than the rate at which data

maintain bit count integrity.

are being read out. When the gated clock generator on

the GC/DM card transmits channel No. 2 address to the

5-50. Figure 5-7 is a simplified block diagram of the

OEG card, the positive stuff request signal is applied

printed circuit card assemblies involved in the overhead

back to the GC/DM card. As a result, one extra gated

service function. Basically, figure 5-7 is an expanded

clock signal GC02 is generated during word 29 in one

version of figure 5-4 with greater emphasis on the

preselected minor frame. A channel card is eligible to

common electronics functions. The overhead service'

receive overhead service once in each major frame

function is initially activated when a rate compare signal

period during a specific

is applied to each channel card from the

Change 5-14