3. RapidIO Lanes > Port and Lane Initialization Sequence
CPS-1848 User Manual
76
June 2, 2014
Formal Status
This document is confidential and is subject to an NDA.
Integrated Device Technology
7. The link-level flow control mode (transmitter or receiver controlled) is negotiated as part of the exchange of status control
symbols. The CPS-1848 always attempts to use transmitter-controlled flow control, and reverts to receiver-controlled flow
control if the link partner does not support the transmitter method.
— To disable the use of transmitter-controlled flow control on a port, set the
.TX_FLOW_CTL_DIS bit.
— The flow control mode that is currently selected is indicated in
Port {0..17} Status and Control Register
8. Once at least seven consecutive status control symbols have been received, and at least 15 have been transmitted, the port
asserts the PORT_OK bit and clears the PORT_UNINIT bit in the
Port {0..17} Error and Status CSR
. Thereafter, the port can
exchange packets and detect/report transmission errors.
The above sequence reliably initializes single or multi-lane links as long as at least one of the redundant lanes in each direction
is working. However, consistent with the RapidIO Specification (Rev. 2.1), the initialization sequence for 4x ports was not
designed to operate correctly when connected to multiple, separate 1x ports on the redundant lanes. This type of configuration
is not supported.
3.4.1
Signal Quality Optimization
The default values for the signal quality settings are sufficient for channels that are compliant with the RapidIO specification’s
short- and medium-reach channel definitions (50 cm with up to two connectors). However, the default signal quality settings
may need to change for long channels and/or high lane speeds.
The CPS-1848 supports two methods for optimizing the signal quality of a lane (see
• Transmit emphasis
• Receiver Decision Feedback Equalization (DFE)
Transmit emphasis changes the characteristics of the transmit signal based on the bit that was previously transmitted, and the
bit that will be transmitted after the current bit. Receiver DFE changes the received signal to reduce electrical effects created
by previously received bits.
Figure 13: Optimizing Lane Signal Quality
Clear error conditions on the link, which may have occurred during link initialization.
Transmitter Pre- and
Post- Emphasis
Settings
Receiver DFE Tap
Adjustments
Tx Link Partner
Rx Link Partner
IDLE2 Comands for Pre- and
Post-Emphasis Adjustment
IDLE2 Command Acknowledgements