Altera IP Compiler for PCI Express - Manual (Page 138)

5–52 Chapter 5: IP Core Interfaces
Avalon-MM Application Interface
IP Compiler for PCI Express User Guide August 2014 Altera Corporation
Figure 5–40 shows the IP Compiler for PCI Express reset logic in Qsys systems.
Pcie_rstn also resets the rest of the IP Compiler for PCI Express, but only after the
following synchronization process:
1. When pcie_rstn asserts, the reset request module asserts reset_request,
synchronized to the Avalon-MM clock, to the Reset Synchronizer block.
2. The Reset Synchronizer block sends a reset pulse, reset_n_pcie, synchronized to
the Avalon-MM clock, to the IP Compiler for PCI Express.
3. The Reset Synchronizer resynchronizes reset_n_pcie to the IP Compiler for PCI
Express clock (pcie_core_clk or clk125_out) to reset the PCI Express Avalon-MM
bridge as well as the three IP Compiler for PCI Express layers with srst and crst.
4. The reset_request signal deasserts after Reset_n_pcie asserts.
The system-wide reset, reset_n, resets all IP Compiler for PCI Express circuitry not
affected by Pcie_rstn. However, the reset logic first intercepts the asynchronous
reset_n
, synchronizes it to the Avalon-MM clock, and sends a reset pulse,
Reset_n_pcie , to the IP Compiler for PCI Express. The Reset Synchronizer
resynchronizes Reset_n_pcie to the IP Compiler for PCI Express clock to reset the PCI
Express Avalon-MM bridge as well as the three IP Compiler for PCI Express layers
with srst and crst.
Figure 5–40. PCI Express Reset Diagram
Note to figure
(1) The system-wide reset, reset_n/avalon_reset, indirectly resets all IP Compiler for PCI Express circuitry not affected by
PCIe_rstn/pcie_rstn_export using the reset_n_pcie signal and the Reset Synchronizer module.
(2) For a description of the ltssm[4:0] bus, refer to Table 5–7 .
System Interconnect Fa
b
ric
Reset_n PCIe_rstn
npor
npor
srst
crst
l2_exit
hotrst_exit
dlup_exit
dl_ltssm[4:0]
Reset_request
RxmResetRequest_o Reset Request
Module
PCI Express
Avalon-MM Bridge
Transaction Layer
Data Link Layer
Physical Layer
IP Compiler for PCI Express
Rstn_i
Reset_n_pcie
Reset Synchronizer
(to Avalon-MM clock)
Reset Synchronizer
(to IP Compiler for PCI Express
Clock)