NEC mPD98410 User Manual page 65

Figure 3-26. Difference in Access to HTT between VPC and VCC (single cast)
Access with Port No, VPI (value in
input cell), and VCI (= 20h)
VCC is assumed even if VPC is specified
if the cell is other than an RM cell with
PID = 01h if VCI = 0 to 1Fh.
(3) Calculating HTT address
In 3.3.4 (2), it is explained that a logical input port number, VPI, and VCI are used to calculate an address when
the Area-A of the HTT is accessed. This section explains how these parameters are used to calculate an
address.
Internally, the µ PD98410 has the following information for each logical input port.
An actual HTT address is calculated as shown in Figure 3-27, based on the above information. In the example
below, NVPC = 11 and NVCI = 8.
CHAPTER 3 FUNCTIONAL OUTLINE
HTT & Control memory
Control memory
Area-B
HTT
Area-A
NVPC Number of valid bits of VPI + Number of valid bits of VCI
NVCI Number of valid bits of VCI
BASE Base address (offset value)
Port No., VPI, and VCI at
output side are known.
Access with Port No., VPI (value in
input cell), and VCI (value of input cell).
VPC or VCC is identified
Port No. and VPI at output side are known.
N
VPC?
Y
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