ASIC with a large enough counter to theoretically count until the heat death of the universe. Counter value is incremented ever 20ns and every second the ASIC will broadcasts an ethernet frame over 100Mbps ethernet with the current counters value, not that anyone is going to be listening for long anyways.

Assuming the universe dies in approximately $10^{100}$ years. If you are patient enough to wait until then there is a hidden easter egg when we eventually overflow.

Quickstart can be found in the documentation.

This design has been tapedout twice on Global foundries 180nm.

First as part of the Tiny Tapeout experimental gf0p3 shuttle chip :

Secondly as part of the full Expresso chip a fully open source Ethernet focused chip, sponsored by wafer.space as part of there second multi-wafer program run.

No need to be scared, the sun will have engulfed our feeble planet long before the counter overflows.

Assuming the big freeze arrives in $10^{100}$ years and we are operating at 50Mhz, we have:

• $50*10^{6}$ ticks per second
• $50*10^{6}*60*60*24$ ticks per day
• $50*10^{6}*60*60*24*365.25$ ticks per year
• $50*10^{6}*60*60*24*365.25*10^{100}$ ticks until the big freeze

So we need a $\log_2(50*10^{6}*60*60*24*365.25*10^{100}) = 382.679718 \approx 383$ sized counter ... at the very least.

To help you sniff your local network traffic and parse the ethernet frame I am providing the packet_receiver program under the tools folder in case everyone has forgotten how to code by then. In case compilers are still a thing you can build it with:

cd tools
make

To run specify the network interface you want to sniff as the first argument, also yes, you need sudo mode.

Eg:

sudo ./packet_receiver wlp3s0

Expected output:

ethernet interface: wlp3s0
wlp3s0 mac address 60:e9:aa:92:dc:7d
asic mac address 00:90:cf:00:be:ef

dst mac ff:ff:ff:ff:ff:ff
src mac 00:90:cf:00:be:ef
ethtype 88b5
counter: 3304579334241
raw pkt: ffffffffffff0090cf00beef88b5feca610047680103000000000000000000000000000000000000000000000000000000000000000000000000000000000000

dst mac ff:ff:ff:ff:ff:ff
src mac 00:90:cf:00:be:ef
ethtype 88b5
counter: 3304629272673
raw pkt: ffffffffffff0090cf00beef88b5feca6100416b0103000000000000000000000000000000000000000000000000000000000000000000000000000000000000

Now it is parsing the counter value as a uint64_t so technically this will only work correctly for the next 11680 years. Now I know this is concerning and you must be shocked at such sloppy engineering practice of knowingly releasing buggy software, I hear you. But let us first let humanity survive the Epochalypse before we start quibbling over this one.

Just open an issue when you encounter the bug, I will fix it if I'm available.

This project is re-using the Teapot Ethernet accelerator wrapper for communicating over 100Mbps Ethernet using a CAT-3/5 cable in full-duplex mode. Here is to hoping someone still remembers how to talk Ethernet by then.

This wrapper works with layer 2 ethernet packets, operating at the level of the ethernet frame. It support two types of packets:

• application packets, ethtype = 0x88B5 sent by the accelerator
• configuration packets, ethtype = 0x88B6 used to set the ASICs MAC address, Vlan IDentifier, and the TX phase selection

All packets whose destination MAC do not match the ASIC's current MAC address will be filtered out. Unless otherwise specified the ASIC's MAC address is 00:90:CF:00:BE:EF (read as Nortel:BEEF).

The end of the universe counter does not listen to any incoming packets (we are all going to be dead soon anyways) and broadcasts the current counter value every second. Like a cute beacon forever reminding the vast emptiness that a group of apes that made religious rituals out of watching cat videos, were once here.

Response

[ dst mac (6 Bytes) FF:FF:FF:FF:FF:FF ][ src mac (6 Bytes) ][ ethtype = 0x88B5 (2 Bytes) ][ magic number (2 Bytes) 0xCAFE ][ counter (48 Bytes) ][ FCS (4 Bytes) ] 
0

Counter values and magic numbers are sent in little endian with a granule size of 1 byte (standard).

Configuration packets are used to set the ASIC's current:

• MAC address
• Vlan ID
• TX data to clock phase offset

These packets are not forwarded to the accelerator, so it does not provide any acknowledgement of its reception. Also due to our area limitations these are not stored and forwarded. Any corrupted packets will result in a corrupted configuration.

Packet:

[ dst mac (6 Bytes) ][ src mac (6 Bytes) ][ ethtype = 0x88B6 (2 Bytes) ][ New MAC (6 Bytes) ][ padding (3 bits)][ VID (12 bits)][ padding (38 Bytes) ][ FCS (4 Bytes) ]
0

Unless otherwise configured application packets use ethertype 0x88B6, the second IEEE 802.3 specified "Local Experimental Ethertype", whose existence linux networking libraries are unaware of. So trust me: it's real.

ASIC's current MAC address, all packets not addressed (dst mac) to this address will be filtered out, and all responses will use this as the source address.

Default MAC: 00:90:CF:00:BE:EF (read as Nortel:BEEF)

In the event a packet is vlan tagged, packets not matching the VLAN ID will be filtered out. If a packet isn't vlan tagged, it is assumed to belong to our current VLAN.

Default VLAN ID: 0xDAD

To compensate for the output data to reference clock offset induced by the delay on the path from the clock input pin, to the tiny tapeout design's data out flip-flop and back to the output pin, the reference clock for the data out flip flop is selectable, allowing us to use a 180 degree dephased reference clock.

This dephasing configuration is captured during reset depending on the state of the tx_phase pin.

Values:

• 0 no phase shift
• 1 180 degree phase shift

Desgin will be using the official microchip LAN8720A daughter board for testing.

This ASIC will be supporting 100Mbps ethernet using the following assumptions:

• PHY will be implemented used the microchip LAN8720A(I) chips
• External network is full duplex - dropping CRS support in asic
• No 10Mbps support
  • disabling auto-negociation
• LAN8720A clk is provided by an external clock that is shared with the ASIC.
• Stream from LAN8720A is assumed gapeless, any packet gaps will trigger the ongoing packet to be tagged as containing an error

This MAC supports:

• jumbo frames up to 9000 bytes
• VLAN tagging (802.21Q)

The MAC will filter out all unicast packets not matching the configured destination MAC address. This implies that all broadcast and multicast packets will be forwarded.

This ASIC is part of a larger project to build fully open-source Ethernet equipement called the Coffee-shop project.

No AI was used by me in the development of this chip.

All code and design decisions are, and will remain, entirely human made.

Thanks to thegreatpotatogod on reddit for inspiring me with such a terrible idea, the Tiny Tapeout project, its contributors, and all the community working on open source silicon tools for making this possible.

This hardware is distributed under the strongly reciprocal CERN Open Hardware Licence Version 2 unless otherwise specified.

Any submission of this design, or derivatives thereof, made through the Tiny Tapeout shuttle program is additionally licensed under the Apache License 2.0 and is exempt from the reciprocal requirements of CERN-OHL-S-2.0 solely for that purpose.