GTX use (in update)

1.XILINX GTX Introduction The GTX is a low-power gigabit transceiver on the Virtex series FPGA, and the GTX operating bandwidth range on the V6 chip is 750mb/s to 6.6GB/S, enabling two-way transmission and transceiver bidirectional independence. The GTX receive and transmit directions are made up of both PMA and PCs, and PCs provides rich physical coding layer features such as 8B/10B encoding, and the PMA is an analog circuit that provides high-performance serial interface features such as pre-emphasis and equalization. 2.GTX Clock selection with the GTX layout on Virtix6 FPGAs, each GTX Qaud contains 4 GTX and 2 pairs of differential clock inputs. When multiple GTX are used throughout the chip, the GTX and clock inputs need to be distributed appropriately. A clock input from a quad can only provide a clock to an adjacent quad, and can only provide a clock input to an adjacent quad, up to a maximum of three quad, and when the entire chip multiple GTX uses the same reference clock input, a reasonable distribution clock input can save the required number of clocks , and provides redundant design for the clock. Therefore, the basic principle is that several GTX of the same physical interface are put together by the same reference clock as the clock input; GTX with different physical interfaces the same reference clock input can be used if the same reference clock is within the drive coverage range . A clock backup can be done in case of conditions; When a clock can cover more than one GTX, considering the uncertainty of the clock drive capability, there is no need to use the limit (one clock drives 12 GTX). In addition, in the GTP of V5, the same reference clock input for multiple GTP is required, and each GTP is used on the clock chain of the input clock (even if it is not required and is instantiated), and there is a non-use GTP in the middle of the two GTP that is not allowed to share the same reference clock. 3.GTX Pre-emphasis and equalization when using a physical interface to the GTX, such as poor signal quality, data loss, checksum error, to improve signal quality, the GTX provides pre-emphasis, equalization, and output amplitude adjustment. pre-emphasis and adjusted output amplitude are used for data transmission direction, and equalization is used for data reception direction . On high-speed serial interface, high frequency component attenuation is more serious than low frequency component, which leads to signal distortion and bad signal quality. By pre-emphasis in the GTX TX direction, the ratio of high-frequency components can be increased, and the magnitude of the pre-emphasis can be chosen by setting the value of txpreemphasis[3:0]. The amplitude can be adjusted to compensate for line attenuation, and the output amplitude can be selected by setting txdiffctrl[3:0]. The receiver-side equalization is used to compensate for high-frequency signals or to select the amplitude of compensation. 4.GTX of debugging means The GTX provides four different types of loopback that can be used to locate which part of the GTX the problem appears in. At the same time, we analyze whether the problem is clock-dependent by observing the PLL clock lock signal of the GTX output.

GTX use (in update)