TMXF28155 Supermapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Data Sheet
June 2002
438
Agere Systems Inc.
19 VT/TU Mapper Functional Description
(continued)
19.6 VT/TU Mapper Receive Path Description
This section describes all necessary functions of the receive logic (see
Figure 40
, right to left):
I
Virtual tributary demultiplexor (VTDEMUX)
I
Virtual tributary pointer interpreter (VTPI)
I
Virtual tributary terminator (VTTERM)
I
Output selector (OUTSEL)
I
J2 16-byte sequence monitor (J2MON)
I
Receive VT/TU signaling (RX_VTSIG)
I
Receive low-order path overhead (RX_LOPOH)
19.7 VT Demultiplexer (VTDEMUX)
The VTDEMUX logic block (in
Figure 40 on page 435
) will perform all necessary functions to decode which virtual
tributary (VT) is active on the data bus.
This block monitors the H4 byte and frames on the H4 multiframe indication. In frame (VT_H4LOMF = 0 (
Table 189
on page 162
)) will be declared following two consecutive, nonerrored multiframe indications. A multiframe indica-
tion consists of four consecutive frames containing a (00, 01, 10, 11) pattern in the two LSBs of the H4 byte. Once
framed, H4 loss of multiframe (VT_H4LOMF = 1) will be declared following the number of consecutive mismatches
in the H4 multiframe indication programmed into bits VT_H4_NTIME[3:0] (
Table 195 on page 165
). Loss of H4
multiframe alignment will generate AIS downstream. A change in H4 multiframe alignment is indicated by bit
VT_H4LOMF_D (
Table 181 on page 158
) and will generate an interrupt unless the mask is set (VT_H4LOMF_M =
1 (
Table 193 on page 164
)).
Bits VT_RX_GRP_TYPE[6:0] (
Table 193
) are programmed to determine whether the incoming tributary is a
VT1.5/TU-11 or a VT2/TU-12.
See
Table 563
on page 436, through
Table 566
on page 436 through page 437, for VT/TU mapping formats.
19.8 VT Pointer Interpreter (VTPI)
The VTPI logic block (in
Figure 40 on page 435
) will perform all necessary functions to support VT/TU pointer inter-
pretation. The following features are implemented:
The pointer interpreter consists of the following states:
I
Loss-of-pointer (LOP-V)
I
VT-AIS (AIS-V) (all ones in V1 and V2)
I
NDF enabled (NDF) (1001, 0001, 1101, 1011, 1000)
I
Normal (NORM) (disabled NDF, normal pointer)
I
Increment (INC) (inverted I bits)
I
Decrement (DEC) (inverted D bits)