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Transmitter PMA Datapath
Table 1-2: Functional Blocks in the Transmitter PMA Datapath
Functionality
Block
• Converts the incoming low-speed parallel data from the transmitter PCS to high-speed
serial data and sends the data LSB first to the transmitter buffer.
• Supports 8-, 10-, 16-, and 20-bit serialization factors.
• Supports the optional polarity inversion and bit reversal features.
Serializer
• The 1.5-V PCML output buffer conditions the high-speed serial data for transmission
into the physical medium.
• Programmable differential output voltage (VOD )
• Programmable pre-emphasis
• Programmable V
CM
current strength
• Programmable slew rate
• On-chip biasing for common-mode voltage (TX V
CM
)
• Differential OCT (85, 100, 120, and 150 Ω )
• Transmitter output tristate
• Receiver detect (for the PCIe receiver detection function)
Transmitter
Buffer
Related Information
Transmitter Buffer Features and Capabilities
on page 1-13
Serializer
The serializer converts the incoming low-speed parallel data from the transceiver PCS to high-speed serial
data and sends the data to the transmitter buffer.
The serializer supports 8, 10, 16, and 20 bits of serialization factors. The serializer block sends out the LSB
of the input data first. The transmitter serializer also has polarity inversion and bit reversal capabilities.
Transmitter Polarity Inversion
The positive and negative signals of a serial differential link might accidentally be swapped during board
layout. The transmitter polarity inversion feature is provided to correct this situation without requiring a
board re-spin or major updates to the logic in the FPGA fabric.
A high value on the
tx_invpolarity
port inverts the polarity of every bit of the input data word to the
serializer in the transmitter datapath. Because inverting the polarity of each bit has the same effect as swapping
the positive and negative signals of the differential link, correct data is sent to the receiver. The dynamic
tx_invpolarity
signal might cause initial disparity errors at the receiver of an 8B/10B encoded link.
The downstream system must be able to tolerate these disparity errors.
If the polarity inversion is asserted midway through a serializer word, the word will be corrupted.
Caution:
Bit Reversal
You can reverse the transmission bit order to achieve MSB-to-LSB ordering using the bit reversal feature at
the transmitter.
Transceiver Architecture in Cyclone V Devices
Altera Corporation
CV-53001
Transmitter PMA Datapath
1-10
2013.05.06