I have a TI-84 Plus Silver Edition graphing calculator that appears to use that EC-U6 plug. Earlier this year my niece was here and none of our USB device-end connectors fit her camera, and now that I think about it, the port was similar to the EC-E6.
The TI-84 manual says "Communication Link:
The TI-84 Plus has a USB port using a USB unit-to-unit cable to connect and communicate with another TI-84 Plus or TI-84 Plus Silver Edition. The TI-84 Plus also has an I/O port using an I/O unit-to-unit cable to communicate with a TI-84 Plus Silver Edition, a TI-84 Plus, a TI-83 Plus Silver Edition, a TI-83 Plus, a TI-83, a TI-82, a TI-73, CBL 2™, or a CBR™ System.
With TI Connect™ software and a USB computer cable, you can also link the TI-84 Plus to a
As future software upgrades become available on the TI Web site, you can download the software to your PC and then use the TI Connect™ software and a USB computer cable to upgrade your TI-84 Plus."
It doesn't say anything about using the port for charging.