TAP Group

A TAP group is a set of TAPs (identified by the first TDI pin if devices are chained together) which share common TMS and TCK signals. TAPs that share TMS and TCK signals can never be operated independently so this grouping is a way to combine them together in a single definition. TAP groups are used to define Subchains when setting up Dynamic Chains.

TAP groups are derived automatically from TDI pins' TDI Driver Settings on the Pin Mapping screen.

XJTAG names TAP groups by putting square brackets around the name of its TDI pin, i.e. [TDI], [TDI2], [TDI3] etc.

Although XJTAG's JTAG controllers have configurable pins, some have limitations which require all members of a TAP group to be within specific ranges of pins on the controller. See the details about multiple TAP configuration on the hardware page for your JTAG controller.

Examples

Example 1: one shared TAP signal

A setup in which

• TDI is driven with TMS and TCK
• TDI2 is driven with TMS and TCK2

will create 2 TAP groups, [TDI] and [TDI2]

Example 2: fully independent TAPs

A setup in which

• TDI is driven with TMS and TCK
• TDI2 is driven with TMS2 and TCK2

will create 2 TAP groups, [TDI] and [TDI2]

Example 3: shared TMS and TCK

A setup in which

• TDI is driven with TMS and TCK
• TDI2 is driven with TMS and TCK

will create 1 TAP group, [TDI, TDI2]

Example 4: mixed configuration

A setup in which

• TDI is driven with TMS and TCK
• TDI2 is driven with TMS and TCK2
• TDI3 is driven with TMS2 and TCK

will create 3 TAP groups, [TDI], [TDI2] and [TDI3] because no two TDI pins share the same TMS and TCK driver pair.