# Problems with JTAG portion of AVR-USB-JTAG **URL:** \ **Category:** MicroMod\ **Tags:** avr-atmel\ **Created:** [October 10, 2005, 2:25pm UTC](https://community.sparkfun.com/t/problems-with-jtag-portion-of-avr-usb-jtag/972 "2005-10-10T14:25:45Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![westveld](https://avatars.discourse-cdn.com/v4/letter/w/977dab/32.png) [@westveld](https://community.sparkfun.com/u/westveld)\ **Post date:** [October 10, 2005, 2:25pm UTC](https://community.sparkfun.com/t/problems-with-jtag-portion-of-avr-usb-jtag/972/1 "2005-10-10T14:25:45Z")
I have one AVR-USB-JTAG and one AVR-MT128 - both Olimex parts purchased from SparkFun on 5/26/05 Problem I’ve had from the start: Programming & single-stepping using JTAG work ok, but when “running” with the JTAG connector hooked up the timing is messed up on the AVR-MT128 application - example - blink program to blink the onboard LED (psudo code) loop1: wait 1 sec led on wait 1 sec led off goto loop1 When hooked to the JTAG it is off for 1 second, but only on for 1/10th of a second… when unhooked from the JTAG - works great - 1 sec off, 1 sec on. Problem I’m having now: Programming still works well, but the JTAG doesn’t work at all - here are the errors I’m getting when trying to start the debug: [http://www.bc-computing.com/ebay/avrerr.png](http://www.bc-computing.com/ebay/avrerr.png) Text version: Loaded objectfile: c:\data\code\avr\avrstudio\osd\osd.obj JTAG ICE Warning: Reading the program counter, an invalid value (0x7FFFFFFF) was received from the device. JTAG ICE Warning: A problem occured while executing this debug command! Please check the connections, the voltage, and the clock system of the target application! Error reading memory IO Address:0 Size:64 Error reading memory REGISTERS Address:0 Size:32 Error reading memory SRAM Address:96 Size:160 Unfortunately I do not have another device to test with to see if it’s the device or the JTAG unit that is to blame… I’m running AVRStudio V 4.11 SP3, I’ve rebooted, unpowered, etc, numerous times. It stopped working on me last night after working in the morning. Any ideas? ---
**Author:** ![westveld](https://avatars.discourse-cdn.com/v4/letter/w/977dab/32.png) [@westveld](https://community.sparkfun.com/u/westveld)\ **Post date:** [October 17, 2005, 3:09am UTC](https://community.sparkfun.com/t/problems-with-jtag-portion-of-avr-usb-jtag/972/2 "2005-10-17T03:09:22Z")
5 volt regulator onboard the dev board must have an issue - voltage dropped to 4.37 when the AVR-USB-JTAG was connected - powering through the EXT2 connector’s power pins (1 & 2) with a normal 7805 solved all the problems. Thanks, Matt