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What is the relationship between the line rate of aurora and its user clock? in order to solve this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

What is the user clock rate of aurora?

When customizing the aurora IP core, we need to choose the frequency of various clocks, including the GT reference clock, the INIT clock and the DRP clock, in which the GT reference clock is from a dedicated port on a dedicated MGT bank, and the others are not necessary.

Aurora ip customized page

Starting from the GT reference clock, a series of clocks can be derived for Transceiver and aurora protocols through a series of clock management units, such as PLL,MMCM, etc. Today's protagonist is very important, user logic side clock USER_CLK! How much is it? From the customized page above, we can see that our line rate is 3.125Gbps, which looks very high, but in fact, the unit is bit! Divided by 8, it becomes 390.625MBps, which is a byte. What if the transmitted data has 32bit? That's 4 bytes? Then the line rate can be converted into 97.65625MQBps, where the QB is QUAD Bytes (that is, double word, DW). If you use a clock to transmit such 32bit data, a clock to transmit a data, a clock of more than 90 M is enough! Note that in the case of no coding, the calculated clock, but the high-speed serial port for data transmission, will be encoded, 8B/10B coding, then the transmission of 32bit data, coding will be 40bit. The line rate is 3.125Gbps, so if a parallel user clock transmits a data, a 78.125m clock is needed.

To verify, generate an example program for the above custom page and simulate it as follows:

Simulated measurement of user clock

To measure the user clock, the 12.8ns clock, isn't the frequency 78.125m? Verify it!

It is concluded below that if 8B/10B coding is used, the user clock is the line rate divided by the encoded user data bit width. The bit width before encoding can be selected on the customized page of IP:

Data bit width selection

After taking into account the coding, it is easy to get the bit width after coding!

What is the source of the user clock for aurora?

In order to get the user clock source of auroa? Let's take a look at the aurora example program! Start with the user logic module and trace its origin layer by layer:

Example program structure

From user_clk_i, to USER_CLK, to GT_CLK, to txoutclk_out, and finally back to the primitive GTXE2_CHANNEL, the TXOUTCLK; receiver module of course the user clock comes from RXOUTCLK.

Final primitive

User clock is not always available, it needs a link path!

Simulation user clock about the line rate of aurora and the relationship between the user clock is shared here, I hope the above content can be of some help to you, if you still have a lot of doubts to be solved, you can follow the industry information channel for more related knowledge.

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