Subchain

A Subchain usually comprises a subset of the JTAG devices in a single TAP Group and a selection of zero or more External Hardware machines.

Alternatively, a subchain may consist entirely of External Hardware machines.

Subchains are used by Profiles as part of the Dynamic Chains configuration to select what participates in a test.

At least one JTAG device or External Hardware machine must be selected for a subchain to be valid.

The order of the JTAG devices cannot be changed from the order defined on the JTAG chain screen.

Subchains are configured in the Advanced Configuration Options tab, found on the Pin Mapping screen.

When profiles are in use, there is no longer a single Test Reset Sequence that applies to the whole circuit. Instead, for each profile, the subchains that it uses are assigned their own Subchain Reset Sequence if they need one. When XJTAG switches to a given profile the reset sequences for each subchain in that profile are run (the order can be configured).