SparkFun Forums

[acarminati]

Hello everyone,
I'm Newbie to the JTAG related stuff, and i'm here to ask some senior's help.
I want to learn about how to control a chip using JTAG, so I bought myself a JTAG adapter, BUS BLASTER v4, to be precise, and I found among my old stuff a platform on which experiment.
I found an old firewall which has as main CPU a Conexant cx82100.
I verified through the datasheet, it have pins dedicated to JTAG function, and I therefore I assumed it could be a feasible target.

Launching OpenOCD, it spawns something like this:

Code: Select all

root@c2:~# openocd
Open On-Chip Debugger 0.8.0 (2014-08-18-16:12)
Licensed under GNU GPL v2
For bug reports, read
	http://openocd.sourceforge.net/doc/doxygen/bugs.html
Info : only one transport option; autoselect 'jtag'
adapter speed: 500 kHz
Info : clock speed 500 kHz
Warn : There are no enabled taps.  AUTO PROBING MIGHT NOT WORK!!
Warn : AUTO auto0.tap - use "jtag newtap auto0 tap -expected-id 0x00000000 ..."
Warn : AUTO auto1.tap - use "jtag newtap auto1 tap -expected-id 0x00000000 ..."
Warn : AUTO auto0.tap - use "... -irlen 2"
Error: auto0.tap: IR capture error; saw 0x0003 not 0x0001
Warn : Bypassing JTAG setup events due to errors
Warn : gdb services need one or more targets defined
Info : accepting 'telnet' connection from 4444
Info : TAP auto0.tap does not have IDCODE
Info : TAP auto1.tap does not have IDCODE
Error: auto0.tap: IR capture error; saw 0x0003 not 0x0001
Warn : Bypassing JTAG setup events due to errors
   TapName             Enabled  IdCode     Expected   IrLen IrCap IrMask
-- ------------------- -------- ---------- ---------- ----- ----- ------
 0 auto0.tap              Y     0x00000000 0x00000000     2 0x01  0x03
 1 auto1.tap              Y     0x00000000 0x00000000     0 0x00  0x00

It seems to me there's something wrong: for example I expected to see something different from 0x00000000 in the IdCode field.
Due to my lack of knowledge I have difficulties on the interpretation of this data.
I noticed however that TDO is is doing some activities:


Can someone help me on this?

Thank you
Regards.
AC

[pmeyeratdatest]

Hi: The TMS sequence does not seem right. I would have expected TMS to pulse high for one cycle, and then after 32 shifts to go high again for two cycles. I can't tell from this what state your TAP is actually in at this point.