TXC-04252AIPQ Transwitch Corporation, TXC-04252AIPQ Datasheet - Page 70

• Manufacturer Part Number: TXC-04252AIPQ
• Manufacturer: Transwitch Corporation

Specifications of TXC-04252AIPQ

• Pin Count: 160
• Screening Level: Industrial
• Package Type: PQFP
• Lead Free Status / Rohs Status: Not Compliant

Ed. 3, December 2000
QE1M
TXC-04252
TXC-04252-MB
TUG-3 NULL POINTER INDICATOR
For STM-1 TUG-3 format, the Quad E1 Mapper has the option to generate and transmit a Null Pointer Indicator
(NPI) for one or more of the TUG-3s, as shown below.
Three control bits (NPIA, NPIB and NPIC in address 010H, bits 2-0) are provided for selecting one or more of
the TUG-3 NPIs. The three control bits are enabled when the MOD1 and MOD0 control bits are 11
(TUG-3/VC-4 format). The NPI consists of three bytes, starting with row 1. The table below shows the bit
assignment for the first two bytes.
The third NPI byte is designated as fixed stuff and is transmitted as zero. The remaining cross-hatched bytes in
the first two columns of the TUG-3 are tristated on the add bus. When a 1 is written to control bit NULLZ in
address 013H, bit 3 and the NPI feature is enabled (i.e., NPIA, NPIB or NPIC is a 1) the bytes following the NPI
bytes are transmitted as zeros. When the NULLZ bit is a 0, the bytes following the NPI bytes are tristated.
Row 1
Row 2
Bit
Proprietary TranSwitch Corporation Information for use Solely by its Customers.
1
1
1
N
P
I
P
O
H
1
1
TUG-3A
2
0
1
DATA SHEET
86
NPI Bit Assignment
3
0
1
NPI Structure
N
P
I
1
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TUG-3B
4
1
0
VC-4
86
5
0
0
N
P
I
1
TUG-3C
261
6
0
0
86
7
1
0
8
1
0