App notes on JTAG?

[mreed]

We are developing a board, will be producing several thousands of them, and they have two STM32L0xx's on them, and some other chips that also have JTAG. I have told the hardware guys that we can combine all the JTAGs into 1 JTAG and save some (much needed) board space. But when I search for an app-note on jtags and STM32L0xx it returns.. everything (because every STM32L0xx has a JTAG). Is there an app note that deals specifically with chaining the JTAGs, how to setup the debugger, etc?

[Tesla DeLorean]

Are you sure the CM0(+) parts have JTAG, because I'm not?

The L0 parts I'm familiar with support SWD only.

The general JTAG approach is to have a common clock and daisy chain TDO into TDI of the next part in the chain. Depending on the debugger you can pick the target device from those identified in the chain.

[mreed]

Yes, your right. I misspoke. We tend to call any processor debug interface a JTAG, even when it's only SWD.

Can SWD be daisy chained?

[mreed]

No. SWD can not be daisy chained. :\

[Uwe Bonnes]

Newer SWD version know at least multi-drop.