Error validating JTAG scan chain

Development Boards MicroMod
1

I have build a JTAG adapter with a FT2232C and the layout from

http://www.fh-augsburg.de/~hhoegl/proj/ … bjtag.html

The USB-Serial converter (Channel B) works fine, but when I try to use

OpenOCD

c:\Programme\openocd-2006re115\bin\openocd-ftd2xx.exe -f

c:\Programme\openocd-2006re115\bin\at91sam7s256-jtag.cfg

the TCK Pin goes low (pulled high with 47k) and remains low until I

disconnect the JTAG interface and OpenOCD returns this error:

Error: jtag.c:1149 jtag_validate_chain(): Error validating JTAG scan

chain, IR mismatch, scan returned 0x3f

I’ve checked all connections but the problem remained :frowning:

My at91sam7s256-jtag.cfg File:

#define our ports

telnet_port 4444

gdb_port 3333

#commands specific to the Amontec JTAGKey

interface ft2232

ft2232_device_desc “Dual RS232 A”

ft2232_layout usbjtag

ft2232_vid_pid 0x0403 0x6010

jtag_speed 2

jtag_nsrst_delay 200

jtag_ntrst_delay 200

#reset_config [combination] [trst_type] [srst_type]

reset_config trst_and_srst srst_pulls_trst

#jtag_device

jtag_device 4 0x1 0xf 0xe

#daemon_startup <‘attach’|‘reset’>

daemon_startup reset

#target <reset_mode> <jtag#> [variant]

target arm7tdmi little run_and_halt 0 arm7tdmi

#run_and_halt_time <target#> <time_in_ms>

run_and_halt_time 0 30

2

If the TCK goes low, and stays low I would recheck the hardware.

Check with a oscilloscope or logic analyser if there are pulses on any of the JTAG signal lines.

Regards,

Magnus

3

I don`t have a Scope at home, but the JTAG function works with a simple Wiggler device (the at91Sam7 Board is ok)

I have checked the FT2232 Board with a microscope. all connections are ok and the serial converter works fine.

4

The TCK is set as an normally low output by the ft2232 driver in openocd, so measured with a voltmeter it will be low unless there are sustained JTAG transfers.

Try reducing the jtag_speed option to 20 or 100 (this is slower)

Magnus