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Hot!I need to interface a PIC32 micro to 1000BASE-SX SFP module

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JonNewcomb
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2020/01/29 03:28:32 (permalink)
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I need to interface a PIC32 micro to 1000BASE-SX SFP module

The problem is that the PIC ethernet MAC will only run MII (Media Independent Interface) at 25Mhz or RMII @ 50MHz.
A 1000BASE-SX can only be used with GMII or RGMII (or even SGMII??) PHY / MAC combination - not supported on PIC32s / Cortex-M 4 F core products. There is no auto-negotiation in the same way as copper and hence a bitstream rate incompatibility.
Has anyone here solved this problem?
I am looking at the MAX24287 Bidirectional Wire-Speed Ethernet Interface Conversion IC.. Has anyone used it before?
The MAX24287 is a microchip product. Can anyone confirm it will solve this common problem? Specifically - will the IC resample the SFP 1GB to allow the second MII parallel interface to operate at 25MHz with a PIC32 micro?

To pre-empt the usual set of questions:
Q) Why would you want to do that?
A) The reason is 60KV optical isolation is required for ethernet
Q) Why not use 100BASE-FX?
A) Modern switches rarely accept this type of SFP module. Media converter is possible but deemed too untidy. 100BASE-FX is getting rare these days. Speed is not an issue for me.
Q) Wifi?
A) Security. Used where even m0bi1e ph0ne5 must be surrendered when you enter the area
 
Please feel free to use this post as a placeholder to share thoughts, ideas, experiences.
Regards.
#1

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    andersm
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    Re: I need to interface a PIC32 micro to 1000BASE-SX SFP module 2020/01/30 00:41:53 (permalink)
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    One question you didn't answer is why a PIC32? There's many Cortex-A devices with GMII (eg. Microchip's SAMA5D3 series), but AFAIK nothing in the PIC32M or Cortex-M4 range. Which isn't too surprising, since they are too slow to do anything useful with gigabit data rates. NXP's Cortex-M7 i.MX RT1170 will have gigE, but it's still in preproduction.
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    JonNewcomb
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    Re: I need to interface a PIC32 micro to 1000BASE-SX SFP module 2020/01/31 07:58:52 (permalink)
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    Its an option, but there are risks changing the micro core:
     * It's a very noisy environment - short circuit test of this 60KV PSU may cause a crash. Clocks can run slower, but the core voltage is lower. (Only recently moved from 5V PICs and that took some convincing internally!)
     * Much of the code is presently tied to the internal micro peripheral set. input capture/timer counter hardware blocks. Porting that is going to be painful. I guess as always, looking for the easy modification to the existing 100BASE-FX ethernet design. If I was starting the design from scratch, well...
     
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    roundrocktom
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    Re: I need to interface a PIC32 micro to 1000BASE-SX SFP module 2020/02/03 08:20:07 (permalink)
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    KSZ9893 three-port switch. 
    RGMII/MII/RMII to the processor;   two Gig MACs
     
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    JonNewcomb
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    Re: I need to interface a PIC32 micro to 1000BASE-SX SFP module 2020/02/07 10:13:32 (permalink)
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    The KSZ9893 will work with 1000BASE-T on PHY1 and PHY2, but 1000BASE-SX (fibre) I'm not so sure.
    There is no provision for the SD (signal detect) and the different encoding required.
     
    In the copper world, this problem is solved by auto-negotiation by the switch - whereas fibre connections don't negotiate! Please correct me if I'm wrong, thanks.
    #5
    mbrowning
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    Re: I need to interface a PIC32 micro to 1000BASE-SX SFP module 2020/02/07 12:25:41 (permalink)
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    The MAX24287 does look ideal for your application. MII on one side and SGMII/1000X on the other. From the features (section 3) "Connects processors with parallel MII interfaces to 1000BASE-X SFP optical modules".
     
    I used a Microsemi (Microchip) VSC8211 recently, and the VSC8211 also supports MII to 1000X (but I used it in media converter mode- 1000X to Cat5).
    #6
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