Device Configuration

Before XJTAG can place a JTAG device into EXTEST, and manipulate pins, it requires information about how JTAG is implemented in that device. This information is provided by a BSDL file, so care must be taken to ensure that each device is associated with the correct BSDL file.

During the initial chain detection, the ID code and Instruction Register (IR) length are determined for each device in the scan chain. The devices found are summarised in the main list-view, displayed in order from the device closest to TDI of the XJLink to the device closest to TDO of the XJLink.

The current BSDL library will be searched for BSDL files whose ID codes match those read from the chain. If a single match is found, this will automatically be chosen. If no matches are found, you can add a matching file to the BSDL library using the View/Edit Library button. If you wish to use a different BSDL Library or create a new one the Select Library and Create New Library buttons can be used respectively. Assigning a new BSDL library will update the list of available matches for each device in the chain.

Devices with multiple BSDL files

Unfortunately, this information read from the chain may not determine the BSDL file uniquely. If multiple matches are found, you are required to choose one. To do this, select the relevant device in the list, and choose a BSDL file from the drop-down box in the BSDL Settings pane. Precisely which file you should use may be dependent on the device package, which is often apparent from the BSDL file name.

Devices with no BSDL file

If there is no BSDL file available for one or more of the devices in the JTAG chain, it is still possible to use the JTAG functionality of the other devices. All devices without BSDL files will be placed into BYPASS mode.

To do this, you must associate an IR length for the device. To do this, select the relevant device in the list, and uncheck the "Use BSDL" checkbox. The system will calculate the possible values for the IR length, and if there are multiple possibilities, you must choose one from the drop-down box in the IR Length pane.

The list of available IR lengths for a device will be recalculated each time a match or IR length is chosen for another device in the list. Thus to be able to change your choice, you will need to click on the Reset This Device or Reset All Devices button to repopulate the drop-down list

Devices/BSDL files without an ID code

Sometimes BSDL files do not have an ID code, these files can only be matched against devices that do not contain an ID code. This will generally be a special case of a device with multiple BSDL files as described above. As the wizard has no ID Code to use as a reference point, all BSDL files that have been added to the library with no ID Code will be matched to such a device.

Devices/BSDL files with an invalid ID code

In this case, all the devices in the chain will have ID codes marked "Invalid". You can still assign a BSDL file, even though it will not match (be careful to choose the correct one). To do this, select a BSDL file from the Browse Library... button in the BSDL Settings pane.