Protocol analysis
R&S
®
RTP
643User Manual 1337.9952.02 ─ 12
the PHY sublayers, i.e. Physical Coding Sublayer (PCS) and Physical Medium Attach-
ment (PMA) sublayer as follows:
●
Adopts full duplex communication of 1000BASE-T and therefore echo cancellation
on a single twisted-pair channel. This feature reduces cabling while preserving the
Ethernet MAC compatibility
●
Adopts Pulse Amplitude Modulation (PAM-3) encoding scheme with the following
encoding techniques:
– Data encoding is carried out via a 4b3b encoder that converts the MII data (4B
- four bits) with 25 MHz clock to three bits (3B) wide of data that is transmitted
during one 33.3 MHz clock period
– Symbol encoding is carried out via a one-dimensional (1D) PAM-3 encoder that
converts the 3-bit groups into pairs of ternary symbols. These symbols are
transmitted using three voltage levels (-1 V, 0 V and +1 V). One symbol is
transmitted in each symbol period
– Data scrambling is carried out via a sidestream scramble to randomize the
sequence of transmitted symbols and avoid the presence of spectral lines in
the signal spectrum
PAM-3 has a higher spectral efficiency that limits the signaling bandwidth to 33.3
MHz instead of 65 MHz to 80 MHz in 1000BASE-T and 100BASE-TX such that
communication occurs in the best part of a twisted-pair channel. This in turn
improves return loss, reduces crosstalk and EMI, allows for a more aggressive
Electromagnetic Compatibility (EMC) filtering and lower cost (often lower quality)
cabling
In terms of the trigger and decoder development, multiple aspects of this protocol are
new, specifically:
●
Sidestream descrambler: Descrambles the randomized sequence of received ter-
nary symbols
●
1D PAM-3 decoder: Decodes the received ternary symbols into groups of three bits
according to a conversion chart
●
4b/3b line decoder: Decodes the groups of three bits (result of ternary pair) back to
groups of four bits of the data stream
13.10.2 100BASE-T1 configuration
13.10.2.1 100BASE-T1 configuration settings
Access: [Protocol] > "Setup" tab > "Protocol" = 100BASE-T1
Make sure that the tab of the correct serial bus is selected.
Ethernet 100BASE-T1 (option R&S
RTP-57)
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