Characteristics of TXD, RXD, PCL, and PDA

(This message was transferred over from our old forum)
Posted August 14, 2015
By Todd DeBoer
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On 3/29/08 fcrembis asked, “What are the characteristics of TXD,RXD,PCL and PDA dongle I/O lines after a”$” is issued to run the target processor? Do they revert to Hi-Z inputs? Are they 5V compliant?”
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(Follow up post)

Answered:

When you enter ‘$’ in ICP mode, the USB-Dongle is put into a special ‘pass through’ mode that passes characters on TXD/RXD in and out of the USB port. Therefore, TXD is driving and RXD is input. Before entering pass through mode, the target processor is reset and PCL and PDA are driven low.