AR# 67991

描述

In relation to the JESD204 IP, what does the rx_start_of_frame represent?

解决方案

The rx_start_of_frame is a 4-bit frame boundary indication. It indicates the byte position of the first byte of a frame in the received data in the following clock cycle.

• When start_of_frame = 0001, the first byte of a frame is in bits [7:0] of the tdata word with the next 3 bytes in bits [31:8].
• When start_of_frame = 0010, the first byte of a frame is in bits [15:8] of the tdata word with the next 2 bytes in bits [31:16]; bits [7:0] contain the end of the previous frame.
• When start_of_frame = 0100, the first byte is in bits [23:16] of the tdata word with the next byte in bits [31:24]; bits [15:0] contain the end of the previous frame.
• When start_of_frame = 1000, tdata contains the last 3 bytes of the previous frame in bits [23:0] and the first byte of a new frame in bits [31:24].

This signal is asserted one cycle before the AXI4-Stream data.

The alignment of the very first valid byte is always in byte 0 if the multiframe size is a multiple of 4, and rx_buffer_delay is a multiple of 4.

(PG066) v7.0 includes information about timing of the rx_start_of_frame and rx_end_of_frame relative to the AXI data (see Figure 2-3 and Figure 2-4):