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US 8,046,650 B2Granted
TAP with control circuitry connected to device address port
AssigneeTexas Instruments Incorporated
InventorLee D. Whetsel
Life of this patent
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Abstract
The disclosure describes a novel method and apparatus for making device TAPs addressable to allow device TAPs to be accessed in a parallel arrangement without the need for having a unique TMS signal for each device TAP in the arrangement. According to the disclosure, device TAPs are addressed by inputting an address on the TDI input of devices on the falling edge of TCK. An address circuit within the device is associated with the device's TAP and responds to the address input to either enable or disable access of the device's TAP.
Claims4
An integrated circuit comprising:
- A. a test data input lead, a test clock lead, a test mode select lead, and a test data output lead;
- B. test access port circuitry including:
- i. a TAP state machine having a test clock input connected to the test clock lead, a test mode select input, and control outputs;
- ii. an instruction register having a test data input connected to the test data in lead, a test data output, control inputs connected to the control outputs, and instruction outputs;
- iii. a data register having a test data input connected to the test data in lead, a test data output, and control inputs connected to the control outputs;
- iv. multiplexer circuitry coupling the test data outputs of the instruction register and the data register to the test data out lead;
- and
- v. control circuitry having an input connected to the test mode select lead, a TAP control input, and an output connected to the test mode select input of the state machine;
- and
- C. device address port circuitry having a test clock input coupled to the test clock lead, a test mode select input connected to the test mode select lead, a test data input connected to the test data input lead, and a control output connected to the TAP control input.
7 more elements
Dependencies are inferred from the claim text.