I'm getting ready to change a board over to 3.3V supply. I've read thru the posts on using the ICD-U40 at 3.3V and the CCS documentation but I'm still a bit confused.
As I understand it, the Vdd pin on the interface is used by the ICD to set the pull-up voltage on the ICSP pins. But I've also read the ICD can power the target (5V only - thru the Vdd pin I assume), which I have been doing. So how does the ICD-U40 know NOT to power my target at 5V when I run at 3.3V? Is there a jumper or something I need to change?
Joined: 27 Oct 2003 Posts: 126
ICD-U40 and 3.3 target - Resolved
Posted: Thu Sep 02, 2004 12:59 pm
I sent an email about this to CCS and got a reply within a hour:
There are two separate issues.
1. The ICD-U40 can supply 5V to your target if you install a jumper inside the unit. As shipped the jumper is not installed so the ICD is powered from the USB bus and you power the target on your own.
2. The ICD-U40 can program and debug targets from 2V to 5V. You must connect the Vdd pin of your target to the ICD-U40 (using the 6 pin cable) so it knows what levels to use.
Some chips have restrictions on doing a bulk erase at low voltages.
Interesting in that I've been running my target off the ICD without knowing about the jumper. Now I'll have to go look to see if it's installed or not....
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