TMXF28155/51 Super Mapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Preliminary Data Sheet
May 2001
432
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 39
, 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 39 on page429
) 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 176
)) will be declared following two consecutive, nonerrored multiframe indications. A multiframe indication
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 182
). Loss of H4 multiframe align-
ment will generate AIS downstream. A change in H4 multiframe alignment is indicated by bit VT_H4LOMF_D
(
Table 168
) and will generate an interrupt unless the mask is set (VT_H4LOMF_M = 1 (
Table 180
)).
Bits VT_RX_GRP_TYPE[6:0] (
Table 180
) are programmed to determine whether the incoming tributary is a
VT1.5/TU-11 or a VT2/TU-12.
See
Table 551
through
Table 554
on
page 430
through
page 431
for VT/TU mapping formats.
19.8 VT Pointer Interpreter (VTPI)
The VTPI logic block (in
Figure 39 on page429
) 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)