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(2) Access to HTT
Section 3.3.2 General discussed how to calculate the address to access the HTT by using a logical input port
number, VPI , and VCI. In practice, however, the address is calculated in the following procedure, because of
the differences between VP connection and VC connection. Figure 3-26 illustrates accessing the HTT in single
cast mode. The procedure for accessing Area-A is the same in multi-cast mode.
<Procedure>
<1>
The HTT is accessed by using the following value. The value read identifies whether the switching mode
(SM) is VPC (VP connection) or VCC (VC connection).
Logical input port number
<2>-1
If the switching mode is a VP connection, the header translation information is assigned to the area
accessed in <1>.
<2>-2
If the mode is VC connection, the HTT is accessed again by using the following value. The header
translation information is assigned to this area (in a mode other than the switching mode (SM)).
Logical input port number
Cautions 1. With a Pre-Defined Channel (Input-VCI = 0 to 1Fh) of a cell other than an RM cell with PID =
01h, the header is translated by means of normal VC connection even if VP connection is
specified by the information on the switching mode (SM).
2. For an RM cell with PID = 01h, refer to 3.3.6 Accessing HTT with RM cell.
64
CHAPTER 3 FUNCTIONAL OUTLINE
Port No.
VPI in input cell header
Port No.
VPI in input cell header
VPI
VPI
VCI in input cell header
VCI
20h
VCI
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