Understanding of Daisy Chain

[ShuxiangCao]

Hi, We are trying to connect a FPGA board we made to current system. While we reading the documents of the daisy chain, we found that for each RJ45 port, there are two differential signals input, daisy0 and daisy1. I guess this signal works like a trigger, synchronizing the collection of boards. But why where are two signals? How does it work? Do we have more detailed documentation about that?

Thanks a lot.

[ejeffrey]

There are actually 4 signals -- two that go "down" the chain, and two that go "up". Only a single channel is actually used, which acts as a trigger to synchronize multiple boards. The way it works is that after programming SRAM and other configurations for all the boards, we first send a register write to all the slave boards to run them in slave mode. Then we send a register write to the master board, which starts, and sends a pulse down the daisy chain. Each subsequent board receives the start pulse from the board above it, starts running its sequence, and repeats the start pulse down the daisy chain. This allows all the boards to be precisely synchronized. I think that is daisy0, but I am not sure.

There is untested support in the latest jump table firmware for sending data "up" the chain from an ADC board and allowing that to control the jump table.

On Sat, Mar 12, 2016 at 3:54 AM, Coxious notifications@github.com wrote:

Hi, We are trying to connect a FPGA board we made to current system. While we reading the documents of the daisy chain, we found that for each RJ45 port, there are two differential signals input, daisy0 and daisy1. I guess this signal works like a trigger, synchronizing the collection of boards. But why where are two signals? How does it work? Do we have more detailed documentation about that?

Thanks a lot.

— Reply to this email directly or view it on GitHub https://github.com/martinisgroup/servers/issues/333.

[ShuxiangCao]

Thanks for your reply. I've checked and looks daisy0 carries the signal.