XChecker Troubleshooting Guide

This section is a simple guide to understanding common issues you might encounter when configuring FPGAs with the XChecker cable.

Improper Connections

WARNING

Connecting the XChecker leads to the wrong signal will cause permanent damage to XChecker internal hardware. You must connect VCC to +5 V and GND to ground.

Always make sure that XChecker leads are connected properly for the mode of operation desired. Refer to the “Cable Connections and Definitions” table and the “XChecker Operation Mode Connections” table. Use the Cable Logic Level of Pins command to display the logic state of the leads. This helps determine connectivity between the target system and the XChecker cable.

For workstations (applies to Sun only), you must have read and write permissions to the port to which you connect the XChecker cable. XChecker might issue a message stating that the cable is not connected to port ttyx. When you see this message, follow this check list.

• The board must have the power on because XChecker uses power from the board.
  
  
• Check the device driver by using the following command string.
  
  ls -l /dev/ttya /dev/ttyb
  
  The result should be the following.
  
  crw-rw-rw- 1 root12,0 month date time /dev/ttya
  
  crw-rw-rw- 1 root12,1 month date time /dev/ttyb
  
  
• Reconnect the XChecker cable to another valid port.
  
  
• Read the /etc/ttyab file. There should be two lines, as follows.
  
  ttya``/usr/etc/getty std.9600'' unknown off local secure
  
  ttyb``/usr/etc/getty std.9600'' unknown off local secure
  
  If you use a port to connect a modem or a remote login, you cannot use that port. The port must be on. Consult your System Administrator if the information the /etc/ttyab file differs from what is listed in the aforementioned list.
  
  

Improper or Unstable VCC

WARNING

As with any CMOS device, the input/output pins of the internal FPGA should always be at a lower or equal potential than the rail voltage to avoid internal damage.

Never connect the control signals to XChecker before VCC and ground are connected. Xilinx recommends the following sequence.

1. Turn off power to the target system.
   
   
2. Connect VCC, ground, and then the signal leads.
   
   
3. Turn on power to the target system.
   
   

Make sure VCC rises to a stable level within 10ms. After VCC stabilizes, the level should be between 4.75 V and 5.25 V.

In the event of power glitches, reset the cable with the Cable Reset command to reconfigure the XChecker internal FPGA device and then reconfigure the target device. For more information, see the “Resetting the Cable” section.