Hi,

Simple question. My target board is using LPC1768 micro. I've decided not to use JTAG pins so on production board every pin related to JTAG is grounded (pull down) to according to FCC rules. I have noticed that my program working on production board is behaves very strange. Program compiles , no error but after transfer to board (isp + flash magic) nothing happen and everything seems to be freezed(I have set a ligh on one of diode in first line after main()). My question is if there is a interference between JTAG in such configuration (does its possible to simply pull-down w/o pragmatically disabling JTAG feature). Same program run fine when its run on mbed board + same peripherials. Please help.

I wouldn't think that you would want to pull the output pins like TDO low? Also I think you would probably want to pull TRST high and not low. Actually when I look at some LPC1768 reference designs, it appears that most of the JTAG pins are typically pulled high through a 10k resistor except for TCK which has a pull-down to GND and the TDO isn't pulled in either direction.

I agree with Adam - most of the JTAG pins should be pulled up via 10k resistors. What have you done with the reset line to the LPC1768? Is the micro stuck in reset?