I finally figured out what was causing the issue.
The 1.2 volt supply was dropping out due to the MAX4995ALAUT current limiting device. The 4995 was set to support up to 600 mA. Either the device is bad or it can not deal with 1.2 volts. I changed the current limit program resistor to allow 700 mA over the recommend amount and it still dropped out. The large current rush may also happen at startup and drop back after the device is running.
I noticed the TMS570 error lin was dropping and the nRST line was constantly cycling. So the CPU was reseting over and over and the JTAG never had a chance.
Need to study the MAX4995 data sheet more and maybe try another MAX4995 which I have. If it still gives trouble I will try wiring around it and see if the 1.2V power supply will support this. I really do not like the pulse width modulated regulator. It is supposed to be very efficient but efficiency comes with some issues on the output voltage.
I shut the MAX4995 off and connected an external 1.2V supply. Then JTAG started working and I can load programs. The 1.2V supply has 190 mA on the meter.
I tried a couple of programs and found the JTAG loads quickly and dropped into debug window now.
Jim’s Blinky program loaded but the LEDs appear to be full on. At least they wen from dim to full on indicating the program was doing something. Probably configuring the outputs as IO and leaving them in a Low state which would turn on the LEDs. I look at the with a scope later and make sure it is not blinking real fast.
I loaded the loop program also. It seems to load as well.
I will work on more test programs later. Time for a break now.
Bob
Photo of 1.2 volt supply and the LEDs on but not blinking yet.
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