Re: [OpenOCD-user] CC13xx

[Hynek S. <ec...@ce...>]

Hi,

I prepared CC1310's JTAG test using MCU connected to JTAG generating 
JTAG sequences and finally I have an idea what could be wrong between 
openOCD and CC1310.

I took two sets of JTAG signals/sequences: one from openOCD (not always 
reliable connection), another from J-Link (reliable connection).
J-Link sequence main differencies:
- it begins always with TAP reset (it is missing with openOCD at the 
very beginning of communication)
- in case of 'irscan' it uses short path from Exit1IR directly to 
UpdateIR (openOCD uses path through PauseIR and Exit2IR)
- writing of CP1=9 is at once (in openOCD, ti-cjtag.cfg divides this 
sequence to more passes through ShiftDR-PauseDR, i.e. CP1=2+2+2+2+1)
- some minor differences on TDI signal in ShiftDR...
- there are not any gaps in communication (openOCD/FTDI adapter has lot 
of gaps there; usually between every config line...)

It seems that the main problem here is the first irscan command (see 
ti-cjtag.cfg). When it ends with Exit1IR-UpdateIR (J-Link method), it 
works always fine. When it ends with Exit1IR-PauseIR-Exit2IR-UpdateIR 
(openOCD method), it sometimes fails. (and because openOCD does this 
connection sequence always three times, it often fails) - I can 
demonstrate it on my testing circuit where adding or removing these two 
states leads to unreliable or reliable communication.
Other differencies seem to be not important and I haven't noticed any 
influence on communication reliability.

My question is: is there any way how to instruct 'irscan' not to go 
through -PauseIR-Exit2IR- but to use short way Exit1IR-UpdateIR?
I tried to look for it in source files: I have found command 
'tms_sequence', but it is set to 'short' by default. So it must be 
somewhere else that irscan automatically ends in PauseIR or Exit2IR state...
I think that changing the first 'irscan' beahviour would help to get 
reliable switch from cJTAG to JTAG on CC1310... but I don't know how to 
verify in on real openOCD...


Best regards,
Hynek