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DP83822IF: 100BASE-FX Register setting and magnetics inquiries

Kazuki Itoh
Genius 10920 points

Part Number: DP83822IF

Tool/software:

Hi team,

1. Could you let me know the recommended register setting procedure for DP83822IF for 100BASE-FX?

Is the procedure below okay?

i) Table 8-24. 0x000A Control Register #2 (CR2) 

Set bit[14] to 0b1(Enable)

ii) Tabe 8-14. 0x0000 Basic Mode Control Register (BMCR)

Set Bit[13] to 0b1(100Mbps)

Set Bit[12] to 0b0(Disable Auto-Negotiation)

Set Bit[8] to 0b1(Full-Duplex)

Also, if the device is configured to 100BASE-FX by registers, is SD_EN assigned to LED_1 pin?

2. Is Force 100 Mbps Link Enable in Table 8-48. 0x0040 Fiber Far-End Fault Generation/Detection Force Bit[13] invalid if it is 0b0?

3. Could you please review the magnetics below is okay?

i) GST5009M LF-TEL (This is the magnetics for 1000BASE-T, but want to consider if it's okay)

ii) TS8121CM HF-TEL

Best regards,

Kazuki Itoh

  • 0
    TI__Expert 6625 points

    Hi Kazuki, 

    1.

    i) Writing register 0x000A to 4100, or as you put it, set bit[14]  of 0x000A to 0b1, should be all that's required to enable 100BASE-FX mode. Since this mode is independent of Auto-negotiation, turning it off through register 0x0000 is not required. 

    ii) The FX_EN strap must be enabled for SD_EN strap to be functional. If configuring through registers, this would not be the case. 

    2. Bit[13] of register 0x0040 is only meant to force a link at 100Mbps and does not indicate current link speed. 

    3. Table 11-1 has a list of tested transformers with DP83822. The parts you mentioned do not seem to be on this list, however, as long as they meet the criteria highlighted in Table 11-2, they should be good. From what information I could gather about these devices online, they seem to meet said criteria.

    Regards,

    Vivaan