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Spy Bi-Wire with multiple devices


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Hi folks,

 

I'm currently deciding on the layout of the debugging connectors. I have a couple of MSP430 controller boards, which I want to debug simultaneously, more or less.

IEEE 1149.1 JTAG builds on a TDI-TDO daisy-chain from board to board to achive that. TI's CCS IDE supports that (I've heard so).

The IEEE 1149.7 extension to this standard builds on a star-topology, where all the signals (TCK, TMS, TDI, TDO) are connected to all devices in parallel. Furthermore, the standard introduces a 2-wire variant (TI's spy bi-wire?), which I find quite attractive for this purpose.

Here is the related document:
http://processors.wiki.ti.com/images/e/e1/IEEE1149.7overview.pdf

 

Now the questions:

Can I connect multiple controllers to the SBW-interface?
Has anyone tried that before?

 

Thanks in advance,
Bass Mati

 

 

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Interesting question. Since SbW is in fact roughly a multiplexed version of JTAG, it should be possible. Though I doubt that it is actually supported. The most difficult part might be to get all controllers to switch to SbW mode, since it requires a very specific and time sensitive sequence to get the pins to go into SbW mode (instead of becoming just a reset pin).

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Now the questions:

Can I connect multiple controllers to the SBW-interface?

Has anyone tried that before?

 

No, this is not possible. Only supported SBW / JTAG serial chain command for MSP430 is BYPASS, nothing else. Parallel SBW / JTAG interfaces (like MSP-GANG) use separate lines for each target device.

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