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AR# 24699

9.1.01i ChipScope Pro - When issuing Shift-DR instruction with TCL JTAG, bad data is returned

Description

If TCL JTAG is used to issue a Shift-DR instruction in read-only mode and in addition if TDI is set to '1', invalid data is returned. This occurs only when using a Platform USB Cable.

Solution

Using Shift-DR in read-only mode and setting TDI to 1 will use fast read, and there is a problem with the way in which fast read is implemented. There are two alternatives to using read-only and setting TDI to 1.  

 

1. If TDI does not matter when shifting out bits, then set TDI to 0.  

2. Alternatively, just use read/write mode and make TDI a buffer filled with constant 0's or constant 1's.  

 

This will be fixed in ChipScope 9.1.02i.

AR# 24699
Date Created 09/04/2007
Last Updated 05/21/2014
Status Archive
Type General Article