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TSB12LV32-EP and TSB81BA3E interfacing with IEEE 1394

Matthew Greci
Prodigy 60 points
Other Parts Discussed in Thread: TSB12LV32-EP, TSB81BA3E, TSB12LV32

Hello,

I currently am using the the TSB12LV32-EP as the Link Layer Controller and the TSB81BA3E as the physical chip for an IEE 1394 connection using a microprocessor. I believe I have both these chips figured out and a general understanding of the IEEE 1394 protocol. However, I do have a few questions.

1) I have read that the TSB81BA3E (PHY) needs to have a clock supplied to it by crystal of speed 49.152 MHz or 98.304 MHz in order to meet IEEE 1394a or 1394b standards. However the TSB12LV32-EP (LLC) says the maximum input clock frequency it can handle is 60 MHz. The clock the PHY receives(of 49 or 98 MHz), is that independent of the clock I give my LLC? Or can I (for testing purposes) give the LLC instructions at any speed? My initial thought was that, no matter what speed you give the LLC, the PHY will use the clock it is given(49 or 98 MHz) and use that clock for data transferring over the port. If someone could confirm this or correct me, that would be very helpful.

2) I do not necessarily need the 1394b speeds of 800 Mb/s but I am wondering if there is a better LLC to use. I just upgraded my PHY chip from the TSB81BA3D and there was some noticeable difference. The LLC is a 2004 model and is the "enhanced product" but there must be a LLC that fully supports 1394b and its speeds.

Please let me know.

Thank you again,

Matthew G

  • 0
    TI__Guru* 76130 points

    Hello,

    1) The 49 or 98 MHz clock should be supplied to terminal LCLK, this terminal is driven by the LLC, so the LLC is the one that is giving this clock, then the 81BA3E outputs also this signal on terminal PCLK, in this way the LLC and the PHY are synchronized on both scenarios, when the LLC is transmitting data to the PHY and when the PHY is transmitting back to the LLC. 

    2) Please visit the following link http://www.ti.com/product/tsb82aa2b

    According with your customer/application we could share a reference schematic, if you don't want to post sensitive information you can email me to elias.villegas@ti.com

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 60 points

    Thank you for your quick reply.

    That makes sense and I am looking at the newer chip. I understand that the LCLK and the PCLK are used for synchronization but I wonder why there is an input for a crystal on the TSB81BA3E. Is the idea that you can use the crystal clock or use the LCLK? (Basically you will only need one).

    However, when I am using 1394a, there is no LCLK in use. What you have said makes sense for 1394b, but in all the 1394a diagrams I see, there is no clock from the LLC to the PHY. Could you give an explanation to why this is? Is this due to when clock is at 98.304 MHz, there needs to be a clock between the chips for synchronization?

    I am ok with using 1394a speeds, but I would like to use a clock at any frequency I choose. Something very slow for testing purposes. I want to be able to send a request at my own speed. Anyway this can be accomplished?

    Thanks again for your help,

    Matthew

  • 0 in reply to Matthew Greci
    TI__Guru* 76130 points

    Hello,

    You are correct, there is no LCLK on 1394a, if you connect the TSB81BA3 to a 1394a LLC then you need to connect PCLK to SCLK.

    You need the external crystal for the TSB81BA3, the LCLK signal coming to the PHY is for data synchronization but the PHY still needs the crystal for its internal oscillator circuits.

    The clock speeds (like 98.304MHz) depends on the Data speed (s100, s200, etc) you can't use a "custom" frequency for transmission.

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 60 points

    Thank you again for your much needed help.

    I would like to send you our schematic for comparing, however I am having trouble creating a properly scaled schematic. Could you send/release the CAD files for the TSB81BA3E and the TSB12LV32-EP? Please let me know.

    Thank you,

    Matthew Greci

  • 0 in reply to Matthew Greci
    Prodigy 60 points

    Ok, I see how that was a dumb question since all the documents were on the TSB81BA3E page, I was looking on the TSB12LV32 page. 

    The schematic is extremely helpful since it has an example for how to use the PHY with the exact LLC. However, the reference sheet is for the TSB41BA3A (the first version) and there has been some revisions to the chip.

    My concern is how to connect the crystal to the TSB81BA3E. In previous versions, there is a clock input and output(X0, X1) that directly connected to crystal, including some capacitors, but in the newest version "E", the X0 was changed to Reserved. Now there is only one terminal to connect the crystal. 

    My first thought was that I should just leave the connection how the reference schematic shows, but when I read about the RSVD pin, it says it should be left unconnected. How should the crystal be connected to the TSB81BA3E?

    Thank you for your help,

    Matthew

  • 0 in reply to Matthew Greci
    TI__Guru* 76130 points

    Hello Matthew,

    The recommendation is to use an external oscillator instead of a crystal, and leave Pin 26 floating.

    Regards.