Product manual

Product Manual - DM991 Series V Family - 204.4092.08 71

3 4 5 6 7 8

Si 0 0 1 1 0 1 1

Note 1

Si 1 A S

Note 1 Note 2 Note 3

Alterned frames

Bit number

Frame containing the Frame

Alignment Signal

Frame alignment signal

2) Bit always set on 1.

3)Remote alarm indication. If operation normal, set on 0, in alarm set on 1. In case the converter

receptor loses frame synch this bit is transmitted in 1.

4) For specific uses: Bits usually set on 1.

Frame wthout FAS

Note 4

Notes:

1) Si – bit reserved for international use. Usually set to 1 except when CRC4 is used as will be seen.

Table 19. Multiframe structure

Besides this basic multiframe, which is always present, there may be other types of multiframe that are

completely independent among them, and superimposed over the basic multiframe:

16.1.1. CRC4 Multiframe

Made up by 16 frames and uses Si bit of timeslot 0 of the frames to perform the Cyclic Redundancy

Check-4 procedure, making it possible to evaluate transmission quality. This multiframe always starts at a

frame that has FAS. The multiframe structure is identified by a six-bit structure known as the CRC4

multiframe alignment signal, found on odd frames. On the last two odd frames, sub multiframe error

signals are transmitted. Bit E of frame 13 (E13) corresponds to the error occurred on sub-multiframe I and

E15 correspond to the error occurred on sub-frame II. On the even frames, which have FAS present, the

four CRC bits calculated from the previous sub-frame are transmitted. Table 20, shows the CRC4

multiframe structure.