Addressable test access port domain selection circuitry TCK logic gate
This disclosure describes a reduced pin bus that can be used on integrated circuits or embedded cores within integrated circuits. The bus may be used for serial access to circuits where the availability of pins on ICs or terminals on cores is limited. The bus may be used for a variety of serial communication operations such as, but not limited to, serial communication related test, emulation, debug, and/or trace operations of an IC or core design. Other aspects of the disclosure include the use of reduced pin buses for emulation, debug, and trace operations and for functional operations. In a fifth aspect of the present disclosure, an interface select circuit, FIGS. 41 - 49 , provides for selectively using either the 5 signal interface of FIG. 41 or the 3 signal interface of FIG. 8.
1. An integrated circuit comprising:
A. test access port domains, each domain having a TDI input, a TDO output, a TCK input, and a TMS input; and
B. addressable test access port domain selection circuitry including
i. linking circuitry having a separate set of domain leads coupled with each TAP domain, each set of domain leads including a TDI output connected to a TDI input, a TDO input connected to a TDO output, and a TMS output connected to a TMS input, the linking circuitry having a set of internal leads including a TDI internal lead, a TDO internal lead, and a TMS internal lead, and the linking circuitry having a control input;
ii. interface circuitry including a TDI input buffer having an output connected to the TDI internal lead, a TDO output buffer having an input connected to the TDO internal lead, and a TMS input buffer having an output connected to the TMS internal lead, the TDI input buffer, the TDO output buffer and the TMS input buffer being separate from one another;
iii. a TCK input;
iv. a logic gate having an input coupled to the TCK input, a clock enable input, and a TCK output coupled to the TCK inputs of the test access port domains;
v. address circuitry having an input connected to the TDI input buffer output, an address clock input, and an address match output;
vi. instruction circuitry having an input connected to the TDI input buffer output, an instruction clock input, and a control output connected to the linking circuitry control input; and
vii. controller circuitry having a clock input coupled to the TCK input, a TMS input connected to the TMS input buffer output, an instruction clock output connected to the instruction clock input, an address clock output connected to the address clock input, an address match input connected to the address match output, and a clock enable output coupled to the clock enable input of the logic gate.
2. The integrated circuit of claim 1 including plural, separate, functional circuits, with each functional circuit coupled with one test access port domain.
3. The integrated circuit of claim 1 in which each test access port domain includes data and instruction registers coupled between the TDI input and TDO output, and a state machine having inputs connected to the TDK input and the TMS input and having outputs connected to control inputs of the data and instruction registers, the data registers being coupled to functional circuits of the integrated circuit.