Difference between revisions of "JTAG Target Connection Issue"
(Created page with "== Problem == No target connection with XDS220 ISO. The VTRef pin on the JTAG header is used by most emulators to sense and detect the target's I/O voltage. Texas Instrument...") |
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The VTRef pin on the JTAG header is used by most emulators to sense and detect the target's I/O voltage. | The VTRef pin on the JTAG header is used by most emulators to sense and detect the target's I/O voltage. | ||
| − | Texas Instruments target board emulation design guidelines (document sprab21 and http://processors.wiki.ti.com/index.php/ | + | Texas Instruments target board emulation design guidelines (document sprab21 and http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide) recommend to connect VTRef via a 100 ohms current limiting series resistor to the target IO power supply. |
The XDS220 ISO however draws more current from the VTRef pin to supply the target side isolation drivers. A 100 ohms series resistor causes too much voltage drop and the XDS220 ISO will fail to connect to the target. | The XDS220 ISO however draws more current from the VTRef pin to supply the target side isolation drivers. A 100 ohms series resistor causes too much voltage drop and the XDS220 ISO will fail to connect to the target. | ||
Revision as of 10:47, 23 August 2017
1 Problem
No target connection with XDS220 ISO.
The VTRef pin on the JTAG header is used by most emulators to sense and detect the target's I/O voltage. Texas Instruments target board emulation design guidelines (document sprab21 and http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide) recommend to connect VTRef via a 100 ohms current limiting series resistor to the target IO power supply.
The XDS220 ISO however draws more current from the VTRef pin to supply the target side isolation drivers. A 100 ohms series resistor causes too much voltage drop and the XDS220 ISO will fail to connect to the target.
2 Solution
Replace the 100 ohms resistor on your target board with a 0 ohms resistor or a ferrite bead with low DC resistance for better noise immunity.
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