User guide

9–4 Chapter 9: Reset and Clocks
Clocks
Cyclone V Hard IP for PCI Express December 2013 Altera Corporation
User Guide
As Figure 9–3 illustrates, the RX transceiver reset includes the following steps:
1. After
rx_pll_locked is asserted, the LTSSM state machine transitions from the
Detect.Quiet to the Detect.Active state.
2. When the
pipe_phystatus pulse is asserted and pipe_rxstatus[2:0] = 3, the
receiver detect operation has completed.
3. The LTSSM state machine transitions from the Detect.Active state to the
Polling.Active state.
4. The Hard IP for PCI Express asserts
rx_digitalreset . The rx_digitalreset
signal
is deasserted after rx_signaldetect is stable for a minimum of 3 ms.
Figure 9–4 illustrates the TX transceiver reset sequence.
As Figure 9–4 illustrates, the RX transceiver reset includes the following steps:
1. After
npor is deasserted, the core deasserts the npor_serdes input to the TX
transceiver.
2. The SERDES reset controller waits for
pll_locked to be stable for a minimum of
127 cycles before deasserting
tx_digitalreset.
1 The Cyclone V embedded reset sequence meets the 100 ms configuration time
specified in the PCI Express Base Specification 2.1.
Clocks
In accordance with the PCI Express Base Specification 2.1, you must provide a 100 MHz
reference clock that is connected directly to the transceiver. As a convenience, you
may also use a 125 MHz input reference clock as input to the TX PLL. The output of
the transceiver drives
coreclkout_hip . coreclkout_hip must be connected back to
the
pld_clk input clock, possibly through a clock distribution circuit required by the
specific application.
Figure 9–4. TX Transceiver Reset Sequence
npor
pll_locked
npor_serdes
127 cycles
tx_digitalreset