Patent ID: 7346821

Claim:
An integrated circuit comprising: A. a substrate; B. a first TDI input pad, a first TCK input pad, a first TMS input pad, and a first TDO output pad, all formed on the substrate; C. TAP domains formed on the substrate, each domain having a domain TDI input lead, a domain TCK input lead, a domain TMS input lead, and a domain TDO output lead, one domain including a second TDO output pad connected to the domain TDI input lead, a second TCK output pad connected to the domain TCK input lead, a second TMS output pad connected to the domain TMS input lead, and a second TDI input pad connected to the domain TDO output lead; D. input linking circuitry formed on the substrate, the input linking circuitry selectively coupling one of the first TDI input pad and any domain TDO output lead to the TDI input lead of a selected TAP domain, and selectively coupling the first TMS input pad to the TMS input lead of the selected TAP domain in response to control signals on control input leads; E. output linking circuitry formed on the substrate, the output linking circuitry selectively coupling the first TDO output pad to the TDO output lead of a selected TAP domain in response to control signals on control input leads; and F. linking control circuitry formed on the substrate and connected in series between the first TDI input pad and the first TDO output pad, the linking control circuitry having control output leads connected to the control input leads of the input linking circuitry and the output linking circuitry.