Device Categories

The Categorised Devices list is sorted into the following types of device:

Test Devices

Test Devices are usually non-JTAG devices which will be tested by XJTAG, such as memories, interface controllers and IO devices. JTAG devices can be categorised to also be Test devices, if it is necessary for XJTAG to also carry out specific functional tests on the device.

Assigning devices as Test will launch the Configure Test Device Dialog.

Logic Devices

Logic devices, such as buffers, encoders, inverters etc. should be assigned as Logic. Refer to the Logic Files screen for information about the types of device that can be classified as Logic. Classifying a device as logic will launch the Configure Logic Device Dialog.

Passive Devices

Passive Devices such as resistors and links should be assigned as Passive. Assigning as Passive will launch the Configure Passive Device Dialog.

Ignored Devices

Devices that will not interfere with the operation of XJTAG should be classified as Ignored. Devices classified as Ignored must not drive whichever test-accessible nets they are connected to, as this will cause conflicts and possible damage to the board during testing.

Click Configure to view or change any notes about selected Ignored devices.

Excluded Devices

Devices which are likely to interfere with the operation of XJTAG's tests, and which cannot be controlled to prevent this happening, should be categorised as Excluded. This will tell XJTAG that it is unsafe to try to operate the nets which the device is connected to. If, however, the device can at least have its outputs controlled or disabled, it may be better to assign the device as a Test device and set a disable value on an appropriate pin.

XJTAG's Connection Test will not drive test patterns on, or read values from, nets which have excluded devices connected.

NB. Categorising devices as excluded has a significant negative impact on test coverage in the circuit. Because of this you should aim to use this category as little as possible.

Click Configure to view or change any notes about selected Excluded devices.

Unfitted Devices

Devices that are not actually fitted on the circuit board, even though they are defined in the netlist, should be assigned as Unfitted.

Marking the devices as unfitted means they are removed from test coverage statistics, which makes the calculated test coverage a more accurate reflection of the board being tested.

Click Configure to view or change any notes about selected Unfitted devices.