CertusPro-NX SerDes/PCS Usage Guide
Preliminary
Technical Note
FPGA-TN-02245-0.81
© 2020-2021 Lattice Semiconductor
49
All rights reserved. CONFIDENTIAL
PMA Controller
PMA Controller block is shared by all modes, as shown in
. PCI Express PCS is connected to PMA Controller
directly, while MPCS is connected to PMA Controller via External PCS (EPCS) interface. The Tx Gear Box and Rx Gear Box
can be used as 2:1 gearing buffer, when the PMA data width is set to no more than 10 bits. PMA Control Logic controls
the calibration and equalization procedures, and monitors the PMA status. PMA Control Logic also implements the
PRBS generation and check blocks that support PRBS7, PRBS11, PRBS23 and PRBS31 patterns. Some registers inside
PMA Controller can be accessed via Lattice Memory Mapped Interface (LMMI). PMA Control Signals are connected to
both PCI Express PCS and MPCS. MPCS implements some synchronization logic between PMA Controller and FPGA
Fabric, considering that PMA Control Signals from PMA Controller are asynchronous. The Data Polarity Invert modules
between PMA and Tx/Rx Gear Box are implemented to invert the data polarity for Tx/Rx path, if necessary.
PMA
PMA Control
Logic
Calibration
FSM
Equalization
FSM
Register
Space
Rx
Gear
Box
Tx
Gear
Box
PMA Controller
EPCS I/F
from PCIe PCS
EPCS I/F
to PCIe PCS
LMMI I/F
to PCIe PCS
to MPCS
PMA Control Signals
PRBS
Gen & Chk
Data
Polarity
Invert
Data
Polarity
Invert
Figure 6.3. PMA Controller Block Diagram
PCI Express PCS
is the detailed block diagram of the PCI Express PCS. PCI Express PCS is designed for PCI Express protocol
only. The Tx Gear Box and Rx Gear Box inside PCI Express PCS are designed for Gen3 speed only, which implements 2:1
gearing logic. 8B/10B Encoder and Decoder are designed for Gen1 and Gen2 speed. 128B/130B is designed for Gen3
speed only. Word Aligner module is for Gen1 and Gen2 speed, and Block Aligner is designed for Gen3 speed. Elastic
Buffer (CTC FIFO) is implemented to compensate the clock difference between the recovered clock and the transmit
clock. PCI Express related registers can be accessed via LMMI.
PCI Express PCS, PMA Controller and PMA constitute PCI Express Media Access Control (MAC) Layer which can be
connected to PCI Express Link Layer Hard IP block via the PIPE interface.