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LispEngineer / EthernetRepeater

A SystemVerilog implementation of a Ethernet Repeater targeting a Terasic DE2-115 and Marvell 88E1111 PHY

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DE2-115 Ethernet Repeater

Copyright © 2023 Douglas P. Fields, Jr. All Rights Reserved.

Overview

My SystemVerilog code is heavily commented for ease of readability.

Ultimate goal:

Build a SystemVerilog system that reads Ethernet packets on one port and reflects them directly out another port, and vice versa, allowing the FPGA to be a bidirectional repeater.

Do all these things without a soft processor.

Learn about constraints in detail, constrain everything, and make sure the timing analyzer is super happy. Figure out the maximum speed you can run the repeater at (the part that copies data between ports).

Initial goals:

  • [DONE - ALL] Build an MDC/MDIO interface to read all the ports.
    • Display them on the 7-segment displays
  • [DONE] Build an MDC/MDIO interface to write (and read) all the ports.
  • [DONE - ALL] Build an interface that sends a simple ARP request packet
    • Calculate CRC
    • Send at 10BASE-T
    • Send at 100BASE-TX
    • Send at 1000BASE-T
  • [DONE] Build an interface that reads a single packet
    • Display information on 7-seg
    • [DONE] Display information on LCD
    • Display information on VGA or DVI
    • Send packet information via USB UART

Extended goals:

  • Build ARP in for fixed IP

    • Respond to ARP requests
    • Make ARP requests
    • Build up an ARP table
    • Read network configuration from EEPROM, flash or SD card

  • Handle ICMP ping requests

  • Build UDP "echo" protocol implementation Echo

  • Handle Ethernet low level stuff

    • Ethernet flow control, pause frame
    • Other stuff using well-known MAC addresses/multicast addresses

  • Send status data via UDP periodically while being a repeater

    • Number of packets received and sent on each port/direction
    • Number of errors, etc., not sent

  • Build a hub/switch with 3+ ports instead of a simple repeater

  • Status outputs

    • Build VGA/HDMI video output that shows state using character mapped display
    • Status reported by UART periodically
    • Audio status output (like a click)

  • Other speeds/interfaces

    • Handle SFP at 1G
    • Handle SFP+ at 10G
    • Handle other interfaces than RGMII

  • Other PHYs

    • HSMC-Ethernet
    • Write a custom "computer" for initializing PHYs with MDIO via a "program"

  • Other FPGAs

    • Cyclone V
    • Cyclone 10
    • Other Intel chips
    • Kintex-7
    • Artix-7

  • Handle 3+ ports and build a hub and/or switch

    • Build a Content Addressable Memory for:
      • IP to MAC
      • MAC to switch port
      • Include age and removing entries by age

  • Build AXI4 interfaces and multiplexer/switch

Other Ethernet Applications:

  • Stream audio via UDP to the board and output via DAC
  • Stream audio input via UDP from the board to a network host
  • Do DSP on network received audio and send it back over network
    • Or out the local DAC
  • Send PS/2 keyboard and/or mouse to the network
  • Send UART or RS-232 to the network and/or from the network

Misc fun:

  • Use the on-board SRAM or SDRAM... for something
    • (Write your own SDRAM controller, of course.)
  • Implement Pimoroni Scroll Hat Mini for status output and button input

Hardware

Terasic DE2-115

This board has two 10/100/1000 copper Ethernet ports connected by a Marvel 88E1111 PHY, capable of MII and RGMII modes (selectable by jumper). The main FPGA is a Cyclone IV. It has a lot of I/O but no digital display - which can be added by HSMC card. Some useful features:

  • Lots of memory: SRAM, SDRAM, Flash, EEPROM and SD card
  • Lots of on-board user I/O: LEDs, 7-segments, buttons, switches, LCD
  • Lots of external I/O: RS-232, USB UART, VGA, Audio, PS2
  • Expansion: GPIO, EX_IO, HSMC, SMA

...and some not very useful stuff like a TV Decoder.

Development Software

  • Quartus Lite 21.1.0 Build 842
  • Questa Intel Starter FPGA Edition-64 2021.2 (previously known as ModelSim)

Current Functionality

  • Reflects received packets back exactly (with newly calculated CRC)

    • Observations with Ubuntu-sent generated packets:
    • Long packets (at least 64 bytes) are reflected exactly
    • Shorter packets sent by operating system (Ubuntu 22 LTS) are received by the FPGA as length 64, padded by zeros, and resent as that length.
    • Easily handles 700 long packets a second
      • ping -f -c 100 -s 10000 -I enp175s0 -r 192.168.10.134 - fragments into 6 maxmimum length packets (1518) plus one 1166
      • Handles 15000 for 1100 packets a second
    • Cannot handle even on packet at 20000
    • Handles 16,000 but not 17,000

  • Ethernet MII Management Interface (MDC/MDIO)

    • Simulation tested in Questa
    • Tested on real PHY for reading & writing manually
    • Initializes PHY at startup and upon reset per 88E1111 timing guidlines
      • (Does not check for 10 cycles of PHY 25 MHz clock)
    • Turns on PHY-side TX & RX clock adjustments including soft reset
    • Outputs configured signal once fully initialized
    • See below for UI interactions

  • RGMII Transmit Capability

    • Works at 10/100/1000 using PLL generated clock at 2.5, 25, 125 MHz
      • And sends data on TXD with DDR encoding at 1000
      • Sends TX_DV and TX_ER via DDR
    • Automatically adjusts transmit speed based on received in-band data speed information
      • Uses a clock multiplexer (takes a few cycles to settle) from Quartus documentation
      • Asserts reset for the transmitter (only) when adjusting clock speed
    • Sends a packet from one of 8 RAM buffers when it gets a FIFO request
      • Each buffer is 2k long so it can handle any non-jumbo frame
      • FIFO request says the RAM buffer to use and the packet length
    • Calculates the CRC on the fly and sends it, using generated HDL

  • RGMII Receive Capability

    • FIFO for putting notifications of fully received packets into
    • RAM buffer for putting full packet data into (excluding preamble/SFD, including FCS/CRC - not checked!)
    • In-Band metadata connected
      • Tested at 10/100 Full/Half and 1000 Full
        • (PHY will not autonegotiate a 1000 Half link with default settings)
      • Shows 1000 speed when no connection (Reg20, bits 6:4)
    • Receives data at all speeds
      • Uses inverted clock on DDR to get 1000 data without an extra cycle latency
      • Tracks the preamble for SFD; does not store preamble or SFD in receive buffer
        • Allows short preambles or missing preamble bytes from the PHY:
        • "Clause 22.2.3.2.2 shows all that is required is that the SFD is received fully and it is correctly aligned at the MII pins. No preamble preceding SFD needs to be conveyed through the MII." Source and of course see the 802.3-2022 spec itself.
        • Handles missing preamble nibbles. Wikipedia says: "The receive data valid signal (RX_DV) is not required to go high immediately when the frame starts, but must do so in time to ensure the start of frame delimiter byte is included in the received data. Some of the preamble nibbles may be lost."
          • Actually, it handles missing preamble bytes; it expects the SFD to come in byte-aligned.
    • Disabled "Bogus" test impementation of receiver to exercise RAM, FIFO
    • DISABLED Displays the first 32 bytes of payload as ASCII characters on the LCD (after the Ethernet header: 2 MACs and an EtherType)

  • Built-in LCD driver

    • Can put a character anywhere with single activation request
    • (Cannot initialize screen yet! Works only if screen initialized by previous programming.)

  • RAM copier - memcopy

    • Copies a set amount of words from one RAM to another RAM with a few clocks latency
    • RAM word sizes must be the same, but address sizes can differ

  • Synchronizer module

    • Variable depth & width
    • Has synthesis attributes for Quartus/Intel to handle it properly

  • Miscellaneous

    • 7-segment driver

Next Steps

  • Make the RAM copier run at a higher speed than bytes can be received so we can empty our buffers faster than we can receive them and keep up with line speed

    • Something at or over 125 MHz would work
    • Or run at 50 MHz and copy 3+ bytes at a time

  • Receive a packet, retransmit it- but also do something with it locally like display it to the LCD or a VGA output

    • Copy it to another buffer concurrently with the first buffer?

  • Add synchronizers to all reset signals that are not synchronous with the main clock. Or maybe just to all reset signals, period?

  • LCD Manager

    • Power-up sequence required

  • Management state machine

    • Query MDIO for state periodically and exports state flags based on the state read
      • Link up & ready
      • Speed
      • Duplex
      • (Unnecessary for RGMII optional in-band state signaling?)
    • Enable and handle interrupts
    • Handle changing transmit speed as receive speed changes (Use a clock multiplexer)

  • Simple RGMII TX interface

    • Handle Interpacket Gap
      • See 802.3-2022 4.4.2 interPacketGap of 96 bits for up to 100Mb/s & 1 Gb/s
      • Important as the FIFO could be kept full
    • Future: Figure out how to parcel out RAM slots
      • Maybe start with a FIFO of all N slots filled up
      • Then as a slot is asked to be sent, re-add it to the FIFO
      • This can fail badly if someone doesn't send a slot, so maybe not a good idea...
    • Add some bus (e.g. AXI4-Lite) for
      • Putting packet data into the transmit RAM slots
      • Adding an entry to the transmit FIFO
    • Allow RAM writes more than 8 bits at a time so it's faster to copy a packet to transmit from receive RAM for the repeater function.
      • Use byte masks - but not really necessary since we don't care if we copy "bad" data that won't be sent after the last byte of the packet

  • Simple RGMII RX interface

    • Check frame CRC
    • Expand RAM size:
      • Allow reads 32 or 64 bits at a time, but still write during RX 1 byte at a time with byte selects
      • Same, but write a word at a time
      • Expand RAM size by 1 bit, when that Nth bit is set it signals end of packet, and the other bits signify things like:
        • CRC error
        • Frame error
        • Then we could send a "Receive begin" message on the FIFO and the receiver could read from RAM the data as it is coming in.
        • Or we could send a "Receive complete" message on the FIFO with the final length and error information
    • Build a streaming output (AXI-Stream?) when we are getting a packet
      • Have an end of packet flag, which shows CRC and framing errors

  • Improved CRC generator specifically for Cyclone IV

    • Build a 3 & 4 entry XOR LUT mechanism to target the Cyclone IV's 4-LUT
    • Rewrite the CRC to use these 3/4-LUTs to reduce the combinatorial depth
    • Reference: Cyclone IV Device Handbook, Volume 1, Section I, Part 2, LE Operating Modes -> Normal Mode, Figure 2-2

  • Enable reduced preamble mode for Management Interface?

  • Simulate the PHY side of the Management Interface (for reads)

  • Simulate the MAC/PHY side of TX/RX

  • Put a decimal counter into the Bogus packet generator

    • Here is one BCD converter
    • Here is a better description

User Interface

  • Red LEDs 15-0: Data read from registers
  • Red LEDs 17-16: LCD:
    • 17 = lcd_busy
    • 16 = lcd_available
  • Green LEDs 5-0: PHY RX in-band status
    • 0 = Link Up
    • 1 = Full Duplex
    • 2 = 10
    • 3 = 100
    • 4 = 1000
    • 5 = RX in-band data differs on H and L edges - happens sometimes
  • Green LED 6: Eth PHY configuration complete
  • Green LED 7: PLL Lock status for 125, 25, 2.5 MHz from 50
  • Green LED 8: Heartbeat
  • SW 4-0: Register address for below (Register decimal 17 is interesting.)
  • KEY 0: Set register address for KEY 1/2
  • KEY 1: Read from stored register to Red LEDs & HEX
  • KEY 2: Transmit fixed Ethernet packet (at SV-defined fixed speed)
  • KEY 3: Reset Ethernet Management & PHY (only, for now)
  • HEX 7-6: Stored MDIO Management Interface register (from key 0)
  • HEX 5-0: Receiver counts
    • 5-4: Count of received frames ended by a "carrier" message (i.e., RXDV 0, RXERR 1)
    • 3-0: The 16 bits read from the most recent receive FIFO: crc error, frame error, 3 bits of buffer number, 11 bits of length
  • LCD: Displays 32 characters of received packet data as ASCII starting after Ethernet frame header (i.e., after 2x MAC & EtherType, preamble and SFD)
    • (This can be off if the PHY omits some preamble nibbles/bytes)

Open Questions

  • During Management Interface idle periods - should I continue to run MDC?

    • Seems unnecessary and a waste of energy

  • Can we get non-aligned packets?

    • Can we get extra bits before the SFD such that the 1011 comes non-nibble or non-byte aligned?

  • Quartus is ignoring my GLOBAL_CLOCK settings for a few of the clocks. This talks about it but doesn't really explain why.

  • If we get RX_ERR (RX_ER, RXERR) with RX_DV, what do we do with the data in that byte/nibble?

    • For now, I am just ignoring it (not adding it to receive buffer)

  • Is there a standard, fault tolerant "in use" system so we can allocate buffers, use them, and release them in a safe fashion?

Known Bugs

  • Have an off by one error on receive packet length because it uses the final byte write position and not the actual length.

  • Lots of timing analyzer issues that don't seem to impact operation: "Critical Warning (332148): Timing requirements not met"

  • Timing analyzer does not like the CRC generator running at 125MHz; compiling gives a Critical Warning

    • Open Timing Analyzer -> Tasks -> Reports -> Custom Reports -> Report Timing Closure Recommendations and use 20,000 paths
    • Suggested setting the Synthesis Optimization to "Speed" - this did not help
    • Suggested turning on Physical Synthesis - which I did in the Fitter Advanced Settings - this also did not help
    • I don't really understand how the paths from count to crc are misbehaving
    • We could try Alex's CRC Generator Here which he says synthesizes well in Quartus

  • Sometimes I have to send the MDIO request a few times to get it to respond differently. I haven't looked much into it. It could be a switch/button problem or an actual internal bug or a PHY limitation?

    • This hasn't happened in a while so maybe it's not a problem anymore.

Recently Fixed Bugs

  • [Fixed] MemCopy:

    • Copies src_len + 1 bytes
      • Off by one error in calculating the last byte
    • Copies wrong bytes
      • Probably because we assert our "start writing" a cycle too soon (but that would account for only one wrong/early byte)
      • We should assign wr_data = rd_data

  • Simulating the RAM-reading requires me to stop using .mif files and start using .hex files - so I need to convert my RAM initialization to .hex.

    • However, if you use a simple .mif file with just a single byte per line, this seems to work well enough - the first RAM byte may be different from .mif file but you can see it in the Questa memory viewer.

Hardware Bugs

  • ETH0 is dead: On my DE2-115, enabling the Ethernet (RST_N to 1) on both ports causes ETH0 to be unreponsive when plugged in, but ETH1 reponds just fine and lights up 1000, DUP, RX lights.
    • I have since purchased a second DE2-115 that seems to have two working ETH ports.

Notes on FPGA Resources / Megafunctions / Hard IP

ALTIOBUF

Intel ALTIOBUF docs

  • Add ALTIOBUF
  • Bidirectional buffer
  • Use open drain output (like I2C bus, MDC is pulled high)
    • From docs: "can be asserted by multiple devices in your system"
  • Do not generate a netlist (we don't use a 3P EDA synthesis tool)
  • Generate the Instantiation Template File (not really needed, it's easy, but whatever)
  • Generate the Symbol File (although we won't use it)

Remember - the inout must be a SystemVerilog wire and not logic or else it won't work.

ALTDDIO_IN

See Cyclone IV Handbook, Volume 1, Chapter 7, Figure 7-7 on the DDR Input Register.

This DDR input buffer has the property that, on posedge inclock, it shows the current value of the high bit and the previous value of the low bit, because the new low bit has not yet come in. So, you need to add a single cycle synchronizer on the dataout_h to align the _h and _l data to the same clock cycle (high then low) if you want to handle those two specifically as a pair.

This is necessary for RGMII, as those specific two bits go together to form the RX_CTL signal. At 1000 speed, the two go together to make a single byte of data transfer as well.

It was necessary to configure the DDR input to use "clock inversion" to receive the _h and _l bytes of the same cycle concurrently. Otherwise, it was necessary to save the high from the previous cycle and the low from the current cycle when processing the data on the positive edge, which created a cycle latency. I do not know how this impacts timing, but the timing analyzer is really unhappy.

ALTSYNCRAM

The readout on this seems to take 2 cycles, not one.

  • Post about it
  • The Megafunction asks "Which ports should be registered"
    • If you choose Read Output Ports: q then it adds a register to the output
    • This seems to require two cycles to read the data:
    • Cycle 1: Set the inputs for reading (read enable, read address)
    • Cycle 2: It sents the output register
    • Cycle 3: You can see the data on the register's outputs

I made two RAMs:

  • rx_ram_buffer - registered q output
  • rx_ram_buffer_fast - unregistered q output (one cycle latency instead of two)

CRC Generator Modules

Used the generated code from this site and made it into SystemVerilog. Source is on Github.

Notes on Ubuntu & Wireshark

  • ethtool

    • ethtool enp175s0 - shows the status of that link
    • ethtool -K _device_ rx-fcs on - accept frames with bad FCS (checksum)
    • ethtool -K _device_ rx-all on - accept all other invalid frames (like runts)
    • ethtool -k _device_ shows all device capabilities
    • ethtool -s enp175s0 autoneg on speed 10 duplex full forces 10BASE-T full duplex
    • ethtool -S enp175s0 shows some statistics
    • ethtool --register-dump _device_ shows a bunch of hex values

  • ip

    • ip link show enp175s0 - shows status of that link
    • ip link set _device_ promisc on - turn on promiscuous mode
    • ip -s link to see summary statistics
    • ip -stats link show enp175s0 shows them for that specific device
    • ip link set enp175s0 mtu 1600 increase the MTU for this link (1500 is default)

  • ifconfig

    • ifconfig _device_ promisc - turn on promiscuous mode

  • arping

    • arping -t enp175s0 -S 10.10.10.10 -B - force an ARP packet out that interface with this made up IP address

  • nstat

  • ss

  • netstat

    • netstat -s

  • sysfs

    • ls /sys/class/net/enp175s0/statistics/ shows all available statistics

  • nmcli (Really no idea about this one)

    • nmcli connection show

  • ping

    • Send exactly one ping on a specified interface to broadcast address
      • ping -c 1 -I enp175s0 -r -b 192.168.3.255
    • Send the longest possible non-fragmented packet
      • ping -c 1 -s 1472 -I enp175s0 -r 192.168.10.134
      • Will be 1514 data bytes plus the 4 byte FCS/CRC
      • (1500 data bytes + 2x6 MAC address + 2 byte ethertype/length + 4 byte FCS = max frame size 1518)
        • ((Don't forget the 8 byte preamble and n-byte interpacket delay))
      • Set a larger MTU using ip above and you can go longer

  • packeth

    • GUI (and CLI?) program to send random Ethernet packets, very useful

  • packit

  • Packet Sender

  • scapy

  • Ubuntu network settings

    • For the wired ethernet, make it quiet like this:
    • Details: Do not connect automatically
    • Identity: Whatever
    • IPv4: Manual at 192.168.0.133/255.255.252.0, no gateway, no DNS
    • IPv6: Disable (just easier for now)
    • Security: None (802.1x disable)
    • (Adding a gateway leads to tons of ARPs for 192.168.1.1)
    • Upon enabling the connection we get a bunch of packets:
      • IGMPv3 join for 224.0.0.251
      • ARP announcement for 192.168.0.133
      • A bunch of MDNS

  • Disable MDNS on wired ethernet (Avahi)

    • /etc/avahi/avahi-daemon.conf and add the interface to deny-interfaces

  • With the network configuration above, and removing MDNS (Avahi), you now get a very quiet interface: Just a few ARP announcements. Then you can just use arping to generate random packets.

  • Little monitor I cooked up:

    clear ; while /bin/true ; do echo -e -n '\E[25A' ; for i in ls /sys/class/net/enp175s0/statistics/ | fgrep -v txxxx_ ; do echo $i cat /sys/class/net/enp175s0/statistics/$i ; done ; sleep 1 ; done`

  • Docs

Wireshark

  • Documents/Tutorials

  • Capture Privileges

    • Or just run as root

  • Seeing FCS?

  • Network Tap

  • Filters

    • eth.type != 0x86dd && eth.type != 0x0800 - remove all IPv6 and IPv4 packets
      • (Generally leaves just ARP and invalid stuff)

  • Wireshark Ethernet options

    • Assume packets have FCS: Always
    • Validate the Ethernet checksum if possible
    • NOTE: receive packets include the FCS, but sent packets do NOT, so doing this will find FCS/checksum errors in all SENT packets

Notes on Test Harness

Ensure Quartus Settings -> Simulation shows Questa Intel FPGA

Do not use $finish; in your simulation - it will quit Questa and you will have to do everything below all over again!

  • Run Questa: Tools -> Run Simulation Tool -> RTL Simulation...
  • To restart simulation: Simulate -> Restart...
  • You can save your waves
  • You can load saved waves with File -> Load -> Macro File... and then choose test1-wave.do

Setting up Quartus to load the Test Harness in Questa

  • See Quick Start documentation section 1.2, figures 3-4
  • Quartus: Assignments -> Settings -> EDA Tool Settings -> Simulation
  • NativeLink Settings -> Compile test bench
  • Click Test Benches... then New
  • Add a name (e.g., testbench_1) and specify the test_whatever as top-level module
  • Add all the file test_whatever.sv and other.sv and mark it as SystemVerilog
  • NOW, when you run the RTL Simulation it will open this by default.
  • You will still need to save the waves as you like them and reload them (per above).
  • When you change things, you still have to right-click & Recompile in the Library
    • This is a long command in VSIM ##> prompt
  • Then you can type at the VSIM ##> prompt restart -f ; run -all

Issues with QuestaSim

  • Questa does not support .mif memory initialization files! It needs .hex files.
    • Quartus says it will convert the file, but my version of Quartus does not do it.

SignalTap

  • To disable SignalTap again, go to Assignments -> Settings -> SignalTap and unclick Enable

Ubuntu Ethernet Monitoring

  • Monitor counts with: clear ; while /bin/true ; do echo -e -n '\E[45A' ; for i in ls /sys/class/net/enp175s0/statistics/ | fgrep -v txxxx_ ; do echo $i cat /sys/class/net/enp175s0/statistics/$i ; done ; echo ; ifconfig enp175s0 ; sleep 1 ; done

.hex files

Examples

Print a .mif file as a Hex dump:

  • srec_cat starting_tx.mif -Memory_Initialization_File -Output - -HEX_Dump

Print a .mif file as an Intel .hex file:

  • srec_cat starting_tx.mif -Memory_Initialization_File -Output - -Intel

Print a .mif file in a nice format:

  • srec_cat starting_tx.mif -Memory_Initialization_File -Output - -Texas_Instruments_TeXT

Convert a .mif file to a .hex file to the screen:

  • srec_cat starting_tx.mif -Memory_Initialization_File -Output - -Intel

Convert a .mif file to a .hex file to another file:

  • srec_cat starting_tx.mif -Memory_Initialization_File -Output starting_tx.hex -Intel

Example Ethernet Frame

This is an ARP ethernet Frame

ff ff ff ff ff ff - to everyone
06 e0 4c DF DF DF - from whoever we are
08 06 - ARP (type/len)
FROM HERE IS ARP
00 01 - Ethernet
00 00 - IPv4 ARP (not 00 00, this is wrong, fixed in the code)
06 - hardware size
04 - protocol size
00 01 - opcode - request
06 e0 4c DF DF DF - sender MAC address (same as above)
10 20 DF DF - our IPv4 Address
00 00 00 00 00 00 - target MAC address (anyone)
ff ff ff ff - target IP address (anyone)
00 .. 00 - trailer (16x 00's)
xx xx xx xx - checksum

ff ff ff ff ff ff
06 e0 4c DF DF DF
08 06
00 01
00 00
06
04
00 01
06 e0 4c DF DF DF
10 20 DF DF
00 00 00 00 00 00
ff ff ff ff
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
43 4B 0B 75 (checksum is sent least significant byte first)

CRC Calculators

DE2-115 and Marvel 88E1111

Docs:

Linux to keep FCS & bad CRCs

Per schematic, only 4 RXD/TXD lines are connected to FPGA from Marvell Alaska 88E1111.

CONFIG wiring pins on DE2-115:

                  Table 32      Table 12
0 - ground        000 (VSS)     PHY_ADR[2:0]
1 - LED_LINK10    110           PHY_ADR[4:3] and ENA_PAUSE; PHY_ADR[6:5] fixed 10
2 - VCC           111 (VDDO)    ANEG[3:1]
3 - LED_TX        001           ANEG[0], ENA_XC, DIS_125
4 - (see below)   011 or 111    HWCFG_MODE[2:0]
5 - VCC           111 (VDDO)    DIS_FC, DIS_SLEEP, HWCFG_MODE[3]
6 - LED_RX        010           SEL_TWSI, INT_POL, 75/50 Ohm
(ENET_VCC2P5 is fed to VDDOX, VDDOH, VDDO. VSSC is fed to ground)

See Table 34 for exact bit details, and Table 35 for meanings:

PHY_ADR[6:0] = 10 10 000
ANEG[3:0]    = 1110 = Auto-Neg, advertise all capabilities, prefer Master
ENA_XC       = 0 = Disable (MDI Crossover)
DIS_125      = 1 = Disable 125CLK
HWCFG_MODE[3:0] = 1011 or 1111 - RGMII or GMII
DIS_FC       = 1 = Disable fiber/copper auto select
DIS_SLEEP    = 1 = Disable energy detect
SEL_TWSI     = 0 = Select MDC/MDIO interface
INT_POL      = 1 = INTn signal is active LOW
75_50_OHM    = 0 = 50 ohm termination for fiber

Looks like RST_N, MDC, MDIO, and INT_N are all pulled high by 4.7k. RSET and TRST_N are pulled low. JTAG is not configured. XTAL1 gets 25MHZ.

JP1/2 on Pins 2-3 will set MII mode; on 1-2 will set RGMII mode (4 bit) This goes to CONFIG4 pin, which can be either:

  • 011 - LED_DUPLEX
  • 111 - VDDO (which is ENET_VCC2P5 in the docs)a

MII Mode: (p.54)

  • 100BASE-TX - TX_CLK, RX_CLK source 25 MHz
  • 10BASE-T - they source 2.5 MHz

Revision M of Marvell spec:

  • 2.2.1 is GMII/MII
  • 2.2.3 is RGMII

Section 1.5 shows the Reset Modes (specifically Hardware & Software reset)

  • Reg 16.3 defaults to active for RX_CLK
  • Hardware reset stops MDIO but software reset keeps it active (!)

2.8 Power management

COMA pin is tied low per schematic

2.9 Management Interface

IEEE 802.3u clause 22 https://en.wikipedia.org/wiki/Management_Data_Input/Output

Per schematics:

  • Eth0 PHY: 101 0000
  • Eth1 PHY: 101 0001

MDIO: Pull-up by 1.5 - 10 kohm

MDC - maximum 8.3 MHz (120 ns period, per 4.15.1)

Preamble = 32 bits of 1; Suppression allows this to become just one 1

It seems a lot like a I2C/IIC interface but with fixed function and fixed read/write size (16 bits).

The picture makes it look like the value is sampled on the rising edge of the clock.

3. Register Description

This contains all the registers details

4. This section contains the timing diagrams

IEEE 802.3-2022

SEE IEEE 802.3-2022 section 22.2.2.13-14 (page 714) and 22.2.4 page 717

(Note: It is not clear to me if the Ethernet CRC has to be sent as part of the data or if the PHY will do that., per Standard 22.2.3. I am guessing the PHY does NOT do that.)

Std Table 22-6 lists the registers. 22.2.4.1.1 says reset cannot take more than 0.5 sec.

22.2.4.5 has the management frame structure

22.2.4.5.5 Transmit PHY MSB first (5 bits) You can always use an address of 00000 if there is only one device connected! 22.2.4.5.6 Also transmit register address MSB first 22.2.4.5.7 TA Turnaround Read: Z then PHY 0 Write: 10 22.2.4.5.8 DATA is transmitted MSB first

22.3.4 MDIO/MDC timing

  • "When the STA sources the MDIO signal, the STA shall provide a minimum of 10 ns of setup time and a minimum of 10 ns of hold time referenced to the rising edge of MDC"
  • "When the MDIO signal is sourced by the PHY, it is sampled by the STA synchronously with respect to the rising edge of MDC."

Learnings

  • Hardware reset will set all register values to default
    • So if you do hardware reset, after setting Register 20 bits 7 & 1, you need to reset them
  • The link down MAC RX interface speed seems to depend on Register 20 bits 6-4, which defaults to 110 on my DE2-115

Questions

ETHERNET-HSMC Card

Schematic says "RGMII Mode"

  • CONFIG 0 - RX 010 PHY_ADR[2:0]
  • CONFIG 1 - LINK10 110 PHY_ADR[4:3] and ENA_PAUSE; PHY_ADR[6:5] fixed 10
  • CONFIG 2 - VCC 111 ANEG[3:1]
  • CONFIG 3 - TX 001 ANEG[0], ENA_XC, DIS_125
  • CONFIG 4 - DUPLEX 011 HWCFG_MODE[2:0]
  • CONFIG 5 - VCC 111 DIS_FC, DIS_SLEEP, HWCFG_MODE[3]
  • CONFIG 6 - GND 000 SEL_TWSI, INT_POL, 75/50 Ohm
  • PHYADR = 10010 - PHY Address
  • ENA_PAUSE = 1 - Enable Pause
  • ANEG = 1110 - (Copper) Auto-neg, advertise all capabilities, prefer Master
  • ENA_XC = 0 - Disable Crossover
  • DIS_125 = 1 - Disable 125MHz clock
  • HWCFG_MODE = 1011 - RGMII/Modified MII to copper (Table 28)
  • DIS_FC = 1 - Disable fiber/copper auto-select
  • DIS_SLEEP = 1 - Disable energy detect
  • SEL_TWSI = 0 - Select MDC/MDIO interface
  • INT_POL = 0 - Interrupt poliarity - INTn is active HIGH
  • 75_50_OHM = 0 - 50 ohm termination for fiber

The HWCFG_MODE could be changed

  • Register 27 Bits 3:0 (Table 28)

    • 0000 = SGMII with Clock with SGMII Auto-Neg to copper
    • 0100 = SGMII without Clock with SGMII Auto-Neg to copper
    • 1011 = RGMII/Modified MII to Copper (Hard reset default)
    • 1111 = GMII/MII to copper
    • After changing, needs a soft reset

  • Set the delays in the PHY - see Page 213 / 4.12.2

    • Register 20.7 = Delay to RX_CLK
    • Register 20.1 = Delay to TX_CLK

Experimental learnings with 88E1111

  • During RST_N (reset) it will not respond to Management Interface.

88E1111 Register Notes

  • Register 0x11 (17) Page 0 - PHY Specific Status Register - Copper
    • Bits 15-14: Speed
    • Bit 13: Duplex
    • In 10/Full it shows:
      • 0010_1101_0000_1100
      • Speed: 10
      • Duplex: Full
      • Page not reeived
      • Speed & duplex resolved
      • Link up
      • Cable length 80-110m (which is funny since it has a 3' cable)
      • MDI
      • No Downshift
      • PHY ACtive
      • Transmit pause enabled
      • Receive pause enabled
      • Normal polarity
      • No jabber
  • Register 0x01 (1) Page 0 - Status Register
    • In 10/Full it shows:
    • 0111_1001_0110_1101
    • 100BASE-T4 incapable
    • 100BASE-T FD & HD capable
    • 10BASE-T FD & HD capable
    • 100BASE-T2 FD/HD incapable
    • Extended status available in Register 15
    • Preamble suppression allowed (management frames)
    • Auto-negotiation complete (bit 5, copper)
    • No copper remote fault detected
    • Able to auto-negotiate
    • Link up (bit 2)
    • No Jabber
    • Extended register capability - yes

88E1111 Controller

Notes on resets:

  • 2.10 says: "The 88E1111 device will be available for read/write operations 5 ms after hardware reset."
    • Unclear if that means for TWSI only or all operations.
  • Table 59, bit 15, says when the software reset is complete, the bit will be cleared
    • So we can monitor for reset complete by polling this
  • 4.8.1 shows Reset Timings
    • Do a reset for 10ms after valid power
    • Do at least 10 cycles of the (Ethernet) clock before deasserting reset
    • Assert reset for at least 10ms during normal operation
    • 5ms after reset ends you can use MDIO

Controller operation:

  • Reset
    • Implement this as hard reset of PHY
  • Initial startup:
    • Start & hold reset 10ms (call it 15 for good measure)
    • Deassert PHY reset
    • Wait 5ms to get to MDIO capability (call it 7.5ms for good measure)
  • Configuration:
    • Set PHY-side TX_CLK/RX_CLK delays (so we can just read/write "synchronously" on the FPGA)
      • Read Register 20 (0x14)
      • Set bits 7 & 1 and write it
      • Confirm those bits are set
      • Read Register 0
      • Set bit 15 & write it
      • Wait n MS for soft reset
      • Read Register 0 every so often until bit 0 is off
    • Indicate "Ethernet Ready"
  • Normal operation:
    • Offer MDIO Mangement Interface so it can handle read/write requests
    • Occasionally read the status and export them as output signals
      • Link connected
      • Speed
      • Duplex
      • (Note: The ETH RX will get this using in-band signaling)
  • FUTURE: Handle interrupts

Misc Quartus Notes

  • VS Code as external editor: "C:\Users\Doug\AppData\Local\Programs\Microsoft VS Code\bin\code.cmd" --goto %f:%l
    • You cannot insert HDL template without using the internal editor, so sometimes this needs to change
  • Questa directory: C:/bin/fpga/intelFPGA_lite/21.1/questa_fse/win64

16x2 LCD

This is now working - see lcd_module - but doesn't do initialization yet.

Crystalfontz CFAH1602B-TMC-JP

Miscellaneous Ethernet Devices

  • BotBlox makes some interesting Ethernet stuff

About

A SystemVerilog implementation of a Ethernet Repeater targeting a Terasic DE2-115 and Marvell 88E1111 PHY

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