10 GbE Transceiver

Block: 10GbE Transceiver (ten_gbe)

Block Author: David George

Document Author: David George

Contents Summary Mask Parameters Ports Description Configuration Transmitting Receiving Addressing LED Outputs Operation

Summary

This block sends and receives UDP frames (packets). It accepts a 64 bit wide data stream with user-determined frame breaks. The data stream is wrapped in a UDP frame for transmission. Incoming UDP packets are unwrapped and the data presented as a 64 bit wide stream.

Mask Parameters

Parameter	Variable	Description
Port	port	Selects the physical CX4 port.
Shallow RX Fifo	rx_dist_ram	Selects shallow distributed RAM rather than BRAM for the RX FIFO. This option should only be used if the application clock is faster than 156.25 MHz. Constant overruns will most likely occur for clock frequency lower than this.
Pre-emphasis	pre_emph	Selects the default pre-emaphasis to use over the physical link. Currently unused.
Differential Swing	swing	Selects the size of the differential swing to use in mV. Currently unused.
Enable Fabric on Startup	fab_en	This will enable the 10Ge interface on start-up, negating the requirement of software intervention.
Fabric MAC Addresss	fab_mac	Sets the default MAC, usually configured by software.
Fabric IP Addresss	fab_ip	Sets the default IP, usually configured by software.
Fabric UDP Port	fab_port	Sets the default UDP Port, usually configured by software.
Fabric Gateway	fab_gate	Sets the default gateway address, usually configured by software.
Enable CPU RX	cpu_rx_en	Optionally disable the CPU receive interface to save 2 BRAMS, if that interface is not required.
Enable CPU TX	cpu_tx_en	Optionally disable the CPU trasmit interface to save 2 BRAMS, if that interface is not required.

Ports

Port	Dir	Data Type	Description
rst	in	boolean	Resets the transmit and receive memories when asserted
tx_data	in	UFix_64_0	The data stream to be transmitted
tx_valid	in	boolean	The core accepts the data on tx_data into the buffer while this line is high
tx_dest_ip	in	UFix_32_0	Selects the IP address of the receiving device
tx_dest_port	in	UFix_16_0	Selects the listening port of the receiving device (UDP port)
tx_end_of_frame	in	boolean	Signals the transceiver to begin transmitting the buffered frame (ie signals end of the frame). This signal must pulse high on the same clock cycle as the final tx_valid signal
rx_ack	in	boolean	Used to acknowledge reception of the data currently on rx_data and signals the transceiver to produce the next 64 bits from the receiver FIFO.
rx_overrun_ack	in	boolean	Used to reset the RX state machine when a RX overrun occurs.
led_up	out	boolean	Indicates a link on the port
led_rx	out	boolean	Represents received traffic on the port
led_tx	out	boolean	Represents transmitted traffic on the port
tx_afull	out	boolean	Indicates that the TX FIFO is almost full
tx_overflow	out	boolean	Indicates that the TX FIFO has overflowed
rx_data	out	UFix_64_0	The received data stream.
rx_valid	out	boolean	Indicates that the data on rx_data is valid (indicates a packet, or partial packet is in the RX buffer).
rx_source_ip	out	UFix_32_0	Represents the IP address of the sender of the current packet.
rx_source_port	out	UFix_16_0	Represents the sender’s UDP port of the current packet.
rx_end_of_frame	out	boolean	Goes high to indicate the end of the received frame.
rx_bad_frame	out	UFix_16_0	Indicates a CRC error on the frame immediately received when asserted simultaneously with rx_end_of_frame.
rx_overrun	out	UFix_16_0	Indicates that an RX buffer overrun when asserted simultaneously with rx_end_of_frame.

Description

This document is a draft and requires verification.

Configuration

This core will typically be configured by software by setting the following OPB registers: MAC, IP, UDP port, ARP table, gateway and fabric enable. However, there are currently parameters to set these values (except for the ARP table) at build time.

Transmitting

To transmit, data is clocked into the TX buffer through tx_data in 64 bit wide words using tx_valid. When sending the final word of data in the packet, simultaneously pulse the tx_end_of_frame line; the transceiver will add a UDP wrapper addressed to tx_dest_ip:tx_dest_port and begin transmission immediately. Note that tx_dest_ip and tx_dest_port are only looked at when tx_end_of_frame is pulsed high, thus the value must be valid for that clock period but is irrelevant otherwise.

The transmit FIFO can only handle frame sizes of up to 8704 bytes, or 1088 64 bit words. As the TX FIFO approaches full, the tx_afull signal will be asserted. This is an indication that the application should stop entering data into the core. If the application overflows the TX buffer, the tx_overflow signal will be asserted. When the overflow is asserted the TX interface will block, requiring a reset (using rst) to return to full functionality.

Receiving

Upon receipt of a packet, rx_valid will go high, with the received data presented on rx_data in 64 bit wide words. You acknowledge receipt of this data using rx_ack, at which point the next data word will be presented. When the end of the packet is reached, rx_end_of_frame will go high. If the a CRC error occurred when receiving the packet, the rx_bad_frame signal will be asserted.

If the RX data overran the RX FIFO, the rx_overrun signal will be asserted along with rx_end_of_frame. When this occurs the RX state machine will block until the rx_overrun_ack is asserted. It is recommended that the rx_overrun be directly connected to the rx_overrun_ack signal.

There is no hard maximum frame size for RX. However, care must be taken not to overrun the rx buffer.

Addressing

To transmit, the IPv4 address is represented as a 32 bit binary number (whereas it’s usually represented as four 8 bit decimal numbers). For example, if you wanted to send all packets to 192.168.1.1, you would enter

as the IP address. The port is represented by a 16 bit number, allowing full addressing of the UDP port range. Ports below 1024 are generally reserved for Linux kernel and Internet functions. Ports 1024 - 49151 are registered for specific applications and may not be used without IANA registration. To ensure inter-operability and compatibility, we recommend using dynamic (private) ports 49152 through 65535.

LED Outputs

The LED lines indicate port activity and can be connected to external GPIO LED interfaces. Bear in mind that even if no packets are being transmitted or received through the Simulink interface block, miscellaneous configuration packets are still sent and may be received by the microprocessor core. This activity will also be reflected on the activity LEDs.

Operation

Apart from configuring the block, the processor is also used to map the routing tables. ARP requests and responses are handled by the CPU.