- VHDL source: psi_common_wconv_xn2n
- Testbench source: psi_common_wconv_xn2n_tb.vhd
This component implements a data width conversion from a multiple N-bits to a N-bits. The sample rate is increased accordingly. The width conversion implements AXI-S handshaking signals to handle back-pressure.
The width conversion does support back-to-back conversions (vld_o/rdy_i can stay high all the time).
The entity does little-endian data alignment as shown in the figure below.
Data alignment
The with conversion does also handle the last-flag according to AXI specification and it can do alignment. To do so, an input word-enable signal we_i exists. Words that are not enabled are not sent to the output. If the input is marked with the last_i flag, the last enabled word is marked with last_o at the output.
Note that with the assertion of last_i at least one byte of the data must be valid (we_i high). Otherwise it would be unclear when last_o shall be assigned.
Last-Handling and alignment
This entity does only do a width conversion but not clock crossing. If a double-clock-half-width conversion is used, psi_common_sync_cc_n2xn component can be used in front of the width conversion.
| Name | type | Description |
|---|---|---|
| width_in_g | natural; | Input data width |
| width_out_g | natural | Output data width |
The ratio in_width_g_g/out_width_g_g must be an integer number and width_in_g _g must be bigger or equal to width_out_g_g.
| Signal | Direction | Width | Description |
|---|---|---|---|
| clk_i | Input | 1 | Clock |
| rst_i | Input | 1 | Reset (high active) |
| vld_i | Input | 1 | AXI-S handshaking signal |
| rdy_o | Output | 1 | AXI-S handshaking signal |
| dat_i | Input | width_in_g | Data signal input |
| last_i | Input | 1 | AXI-S handshaking signal |
| we_i | Input | width_ing/width_out_g | Input word-enable. Works like byte-enable but with one bit per input-word. At least one word must be enabled together with the assertion of InLast |
| vld_o | Output | 1 | AXI-S handshaking signal |
| rdy_i | Input | 1 | AXI-S handshaking signal |
| dat_o | Output | width_out_g | Data signal output |
| last_o | Output | 1 | AXI-S handshaking signal |