AR# 47509

Description

Solution

If the function is pipelined, or if the top-level loop is pipelined with the -rewind option, an additional output port ap_ready is created to indicate when new inputs can be applied.

If inputs can be continuously streamed, ap_ready is no longer necessary and will be optimized out. 

In Vivado HLS 2012.3 and later, ap_ready will always be generated except in the following conditions:

• If the design is combinational.
• If users set the function protocol to ap_ctrl_none.
  

In Vivado HLS 2012.2 and before, ap_ready will be generated in the following scenarios: 

• For functional pipelines
• For loop pipelines with a "-rewind" option.

Notes: 

Vivado HLS generates ap_ready only when it can be pipelined. 

If users try to apply a pipeline directive to a non-pipelinable design, ap_ready is not generated.

• Do not generate ap_ready for loop pipelines without "-rewind"
• Do not generate for dataflow designs.
• Do not generate ap_ready when "ap_ctrl_none" is applied
• Only generate ap_ready at top-level.

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