Loopback Function - NEC UPD98413 User Manual

3.8 Loopback Function

The two types of loopback modes are supported. These modes can be selected by using the MDPGEN register.
(1) Equipment Loopback
The data input to the transmission side of the ATM/POS interface is looped back at the µ PD98413 internal, and is
output from the reception side of the ATM/POS interface. When loopback is set, the loop data is not output to
the transmission line side. Instead, a frame that is mapped Line AIS frame is transmitted. If the ELPOM bit of
the MDPGEN register is set, the loop data can also be sent to the transmission line.
Tx SOH
Processor
Rx SOH
Processor
(2) Line Loopback
In this mode, the data input from the reception side of the line interface is returned at the µ PD98413 internal and
output from the transmission side of the line interface.
TDOT0/
TDOC0
RDIT0/
RDIC0
SDT0
110
CHAPTER 3 FUNCTIONAL OUTLINE
Figure 3-34. Equipment Loopback
Tx ATM
Processor
Tx POH
Tx POS
Processor
Processor
Rx ATM
Rx POH Processor
Processor
Rx POS
Processor
Figure 3-35. Line Loopback
Tx PLL
Lock state
CDR
CNT
PRELIMINARY
Tx FIFO
Rx FIFO
MUX 0
8:1
DEMUX 0
1:8
SD
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