Data Sheet
June 2002
TMXF28155 Supermapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
449
Agere Systems Inc.
19 VT/TU Mapper Functional Description
(continued)
19.14.3 Virtual Tributary Generator (VTGEN)
The VTGEN logic block (in
Figure 40 on page 435
) performs all functions necessary to map all possible DS1/E1
inputs to the appropriate VT/TU structure. This includes VT/TU pointer generation, positive/negative stuffing,
VT/TU overhead generation/insertion, and DS1/E1 data insertion. The following features will be implemented:
I
This logic block will support the following modes of operation:
— Asynchronous
— Byte-synchronous
— Bit-synchronous
19.14.4 Pointer Generation
I
The pointer generator will support the following features when operating in asynchronous or bit-synchronous
mode:
— If transmit AIS-V is not requested, the following requirements apply:
1. A fixed pointer value of decimal 78 is generated for VT1.5/TU-11 mappings.
2. A fixed pointer value of decimal 105 is generated for VT2/TU-12 mappings.
3. The VT size field will be set to binary 11 for VT1.5/TU-11 mappings.
4. The VT size field will be set to binary 10 for VT2/TU-12 mappings.
5. The new data flag (NDF) is set to binary 0110 for VT1.5/VT2 mappings.
6. V3 and V4 are set to the selected overhead default (SMPR_OH_DEFLT (
Table 77 on page 70
) in the
microprocessor interface block) for all mappings:
— If transmit AIS-V is requested, V1~V4 will be forced to 0xFF.
— Bit stuffing, using the C and S bits, will be performed based on the fullness of the elastic store.
I
The pointer generation will support the following features when operating in byte-synchronous mode:
— If transmit AIS-V is not requested, the following requirements apply:
1. The pointer value is generated based on the location of the incoming frame sync for VT1.5/VT2 mappings.
2. The VT size field is set to 11 for VT1.5/TU-11 mappings.
3. The VT size field is set to 10 for VT2/TU-12 mappings.
4. The new data flag (NDF) is set to 0110 for normal VT1.5/VT2 mappings. If an NDF is requested, the NDF
will be set to 1001 (binary).
5. If an increment is requested, the pointer bytes, V1 and V2, are programmed with the I bits inverted. The
pointer action byte, V3, will be programmed to the selected default (microprocessor bit
SMPR_FXD_STFF_DEFLT (
Table 77 on page 70
)), as well as the byte directly following V3. However,
when incrementing from 139 to 0 for VT2 mapping, the pointer generator sends out NDF-V indication with
the correct pointer (0) instead of the increment indication.
6. If a decrement is requested, the pointer bytes, V1 and V2, will be programmed with the D bits inverted. The
pointer action byte, V3, will be programmed to actual customer data. However, when decrementing from 0
to 139 for VT2 mapping, the pointer generator sends out NDF-V indication with the correct pointer (139)
instead of the decrement indication.
7. The V4 byte will be programmed to the selected overhead default (microprocessor bit SMPR_OH_DEFLT)
for all mappings.
— If transmit AIS-V is requested, V1~V4 will be forced to 0xFF.
Overhead Byte Generation (V5, J2, Z6/N2, Z7/K4, and O Bits).
This portion of the VTGEN logic block will gener-
ate and insert the V5, J2, Z6/N2, and Z7/K4 overhead bytes into the appropriate virtual tributary. O bits are only
accessible in the asynchronous and bit-synchronous modes.