Maximum frequency inputs of Zedboard PMODs

Question

Hi, I am new to the Zedboard. I want to use an ADC with SPI 5MHZ throughout, which means SDO will reach to around 100MHZ with 16bits. Then, I want to use PMODS JA-JD to receive the data from the ADC. What worries me is that could Zedboard PMOD pins are available to receive such inputs with 100 Mhz? I know the I/O banks of FPGA in the PL side can reach 2-4 times of the main clock, but here the problem is the path from Zedboard Pmod pins to the PL GPIO blocks.

Could someone help me? Thanks so much!!

drozwood90 · Accepted Answer

Hi there, On Zedboard, the limit is going to come up in the connector. It is not a high speed connector. A quick Google search and you should be able to locate the PMOD specification. It is maintained by Digilent. https://reference.digilentinc.com/_media/reference/pmod/digilent-pmod-interface-specification.pdf According to that: "The Pmod interface is not intended for high frequency operation, however, using RJ45 connectors and twisted pair Ethernet cable, signals have been sent reliably at 24Mhz and distances of up to 4 meters." If you are careful, you can probably go higher, but you will need to check with Samtec as well as determine the constraint for the SI related to the board trace lengths and package delays - as you will start hitting SI issues. On Avnet created boards, we have hit speeds in the low 100's of MHz, but that was using special cables, routed boards, etc. on PIcoZed. I cannot say that the Digilent routed board would operate at those speeds. If you really want high speed, use the FMC. That is why it is there. The Vita57 spec calls out " signaling speed of 2 Gbps" for the IO and much higher for transceivers. I do not believe the ZedBoard has transceivers, but I think 2Gbps far exceeds what you are calling out. --Dan

longgang · Answer

Hi Dan, Thanks for the reply. I think this is what I am looking for. I read through the hardware user guider of Zedboard. It only mentions that the JC1 and JD1 support 525Mhz LVDS, but no information about JA and JB. Since I want to use all the Pomds on the zedboard around 100MHZ for multi-channel ADC/DAC, JA and JB really confused me. I think I need to create a PCB design with an FMC adaptor to achieve my applications. Longgang

Maximum frequency inputs of Zedboard PMODs

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