HS/DSL Project Yael GrossmanArik Krantz Implementation and Synthesis of a 3-Port PCI- Express Switch Supervisor: Mony Orbach

Project Specifications We will implement:  3 - port switch for PCI-Express  1 upstream, 2 downstream full-duplex ports  Up to 2.5 Gbit/sec transfer rate  CRC support at the DLL layer  Independent packet handling per port  Packet routing between ports through lookup tables

 Send Queue 1 and 2 (SQ1, SQ2) Contain packets routed to current port from the other two switch ports. We have one buffer for each queue in order to prevent simultaneous memory write.  ACK/NACK Queue (ACKQ) Used to store DLLPs for each received TLP while they await sending.  Replay Buffer(RB) Contains all the packets that have been sent on the outgoing queue and have not yet received an ACK.  Send/Receive Pipelines Includes logic for incoming and outgoing packets.  Routing Mechanism Includes an independent copy of the routing table. Local/Global Mechanisms  Packet Storage in Common Memory Space Enables fast packet forwarding between ports  Global Initialization at Boot Time Initialize routing tables with system layout. Local Global

Receive Flow  This mechanism is applied per port.  It displays the sequence of actions that the switch executes on a received packet.  Packet is received on incoming lane  Packet type is determined and CRC check is performed  According to packet type (DLLP or TLP), we take appropriate action.

CRC Logic Block Route packet and Enqueue (TLPs) Continue ACK/ NACK Send Logic (TLPs) Replay Buffer Logic (DLLPs)

Return

Send Flow  This mechanism is applied per port.  It displays the sequence of actions that the switch executes in order to send a packet on the outgoing lane.  The switch contains 4 buffers with packets to be sent: SQ1, SQ2, ACKQ and the Replay Buffer.  It will decide from which buffer to select the packet to be sent (if they aren’t empty), and send it on the outgoing lane.

Completed Tasks Detailed design  Data flow diagram (transmitter/ receiver) for ports  Queue and buffer structure for ports  Packet handling algorithms System block design  Completed most of higher-level block design  Work in progress on lower-level blocks Preparation for VHDL coding  Learned to work with HDL designer  Learned VHDL (basic level)

Semester Plan Complete design for all sub-blocks 3 weeks  Routing/lookup table mechanism  Arbitration logic  Send Queue implementation  Concurrency issues in queue access  Deal with unresolved issues such as: - Interaction with Physical Layer - Understand memory segmentation VHDL design 1 week  Division of the system into interconnected entities  Definition of appropriate architecture per entity  Preparation for VHDL implementation Exam period break…4 weeks VHDL design 1 week  …continue design (and start coding).