How to define the register depth if I add an IO register for the top-level scalar

[araongao2015]

Hi,

When I try to add an IO register for the top-level scalar, there is a parameter -depth. But I find it can only be used for ap_fifo to set the depth of FIFO. So I want to know can I set the depth of register to create a cascaded registers.

Thanks,

Regards

[u4223374]

Isn't this just a register array? For that you just need to put an array on the interface.

[araongao2015]

Hi,

Below is the GUI of adding IO register in Vivado HLS.  I just want to add register to an IO. The main issue is how to set the depth of register. Here the -depth cannot be used to get this goal.

Thanks,

Regards

[pupkin · Accepted solution]

It is all about implementing handshaking signals xxx_vld and xxx_ack (default ap_ctrl_hs mode).

With no register, handshaking is trivial.

With 1 register, handshaking is a bit more complicated (at any time there is either 0 or 1 value "in transit")

With >1 register depth, you'd need a proper FIFO to get the handshaking signals right.

Regards,

VP

[araongao2015]

Hi @pupkin

I get a clear perspective of it now. Thank you for your explanation.