
11–2 Chapter 11: Deterministic Latency PHY IP Core
Auto-Negotiation
Altera Transceiver PHY IP Core November 2012 Altera Corporation
User Guide
The data that the Deterministic Latency PHY receives data on its FPGA fabric
interface employs the Avalon Streaming (Avalon-ST) protocol to transmit and receive
data. The Avalon-ST protocol is a simple protocol designed for driving high
bandwidth, low latency, unidirectional data. The Deterministic Latency PHY IP Core
also includes an Avalon Memory-Mapped (Avalon-MM) interface to access control
and status registers. This is a standard, memory-mapped protocol that is normally
used to read and write registers and memory. The transceiver reconfiguration
interface connects to the Altera Transceiver Reconfiguration Controller IP Core which
can dynamically reconfigure transceiver settings. Finally, the PMA transmits and
receives serial data.
f For more information about the Avalon-ST and Avalon-MM protocols, refer to the
Avalon Interface Specifications.
Auto-Negotiation
The Deterministic Latency PHY IP Core supports auto-negotiation. When
auto-negotiation is required, the channels initialize at the highest supported
frequency and switch to successively lower data rates if frame synchronization is not
achieved. If your design requires auto-negotiation, choose a base data rate that
minimizes the number of PLLs required to generate the clocks required for data
transmission. By selecting an appropriate base data rate, you can change data rates by
changing the divider used by the clock generation block. Table 11–1 shows an
example where setting two base data rates, 4915.2 and 6144 Mbps, with the
appropriate clock dividers generates almost the full range of data rates required by
the CPRI protocol.
1 You can use PMA Direct mode in the Transceiver Native PHYs for CPRI applications
that require higher frequencies. For more information refer to the following
documents:
■ Arria V Transceiver Native PHY IP Core
■ Stratix V Transceiver Native PHY IP Core
Table 11–1. Recommended Base Data Rate and Clock Divisors for CPRI
Data Rate (Mbps) Base Data Rate (Mbps) Clock Divider
614.4 4915.2 8
1228.8 4915.2 4
2457.6 4915.2 2
3072.0 6144.0 2
4915.2 4915.2 1
6144.0 6144.0 1
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