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TMDXRM46HDK: Designing a PCB for safety applications

Christian Gabor
Prodigy 70 points
Part Number: TMDXRM46HDK
Other Parts Discussed in Thread: RM46L852, HALCOGEN

Hello,

I have evaluated the RM46L852 with the Hercules RM4 MCU development kit (TMDXRM46HDK) and now want to build a PCB that incorporates the RM46L852 processor for safety functions following the IEC 61508 standard.

It is my understanding that the development kits are for test purposes only, so to actually use the RM46L852 for a safety function I will need to design my own PCB. With the Hercules RM4 MCU, it was easy to get the desired functionality up and running; however, designing a PCB from scratch adds a lot more complexity. I have not found much information on how to actually accomplish this.

Desired specs:

  • The PCB needs to connect to magnetic safety switches to detect if they are open or closed.
  • The PCB needs to communicate through USB or UART RS232.
  • I intend to program the board using an external XDS100v2 Emulator connected to pins

Questions:

When designing my PCB, how do I configure the board to program the RM46L852 processor? Will I be able to use CCS and HALCoGen on this PCB? Additionally, how would I configure the board to allow UART or USB communication? It seems that on HDK board, the UART (SCI) only goes through the JTAG connection. Is there a way to enable SCI communication without having the JTAG emulator present?

Also, to ensure that IEC 61508, I know that I will need to include a TPS65381 voltage monitor for the RM46L852, but what other considerations do i need to take into account to ensure the PCB complies with safety standards?

Thanks,

Chris

  • 0
    TI__Guru**** 197356 points

    Hello Chris,

    1. You need to route the JTAG signals to a 14pin or 20pin JTAG header based on the emulator you used.

    2. You can use TI code composer studio and emulator to program the RM46x processor. Please find the development tools (IDEs and emulators) for Hercules RM46x MCU:

    3. We have XDS100V2 built on HDK board. You can add one uart transceiver on board and a header for UART signals.

    Regards,

    QJ

  • 0 in reply to QJ Wang
    Prodigy 70 points

    Thanks QJ,

    As a followup question, how do I connect the 20pin JTAG signals to the RM46L852 itself? Are there any reference documents that would help me design this PCB?

    Chris

  • 0
    Genius 4675 points
    Take a look at parts 2 and 3 of IEC61508.

    For the PCB, you'll see a large list of requirements depending on your targeted SIL level.

    In basic terms, (and highly dependent on your application), you'll need to choose components so as your PCB meets the PFH, SFF or DC requirements of the SIL level your targeting.

    If the DC or SFF is too low, you can improve this with software, if the PFH is too low you can improve this by choosing better components or improvements such as dual channels.

    You'll also need to complete FIT (Fault Injection Testing) for each failure mode of each component and have this documented. Search for FMEDA in 61508.

    There are a host of other issues, so make sure you have a copy of IEC61508.

    Hope this helps.
    Stomp!.