A scan chain may be formed throughout an integrated circuit in which the scan chain is coupled to a set of pins via bi-directional input/output (I/O) buffers. A test pattern may be received from an external tester using the set of I/O pins and buffers operating in parallel. The test pattern is scanned into the scan chain using a shift clock operating at a first rate. The test pattern is then provided to combinatorial logic circuitry coupled to the scan chain. A response pattern is captured in the scan chain and then scanned from the scan chain using a shift clock operating at a second rate that is slower than the first rate. The response pattern is provided to the external tester using the same set of I/O pins and buffers operating in parallel.

A built-in self-test (BIST) circuit is disclosed which integrates the functions of pins for test input data TDI, test output data TDO and an analog input signal VPP into a single digital/analog input/output module, and internally produces a test trigger signal STROBE and a digital-analog conversion signal ANA. In addition, when there is a need to power the test chip with a voltage or current, a data generation circuit of the BIST circuit can generate a digital-analog conversion signal to change an operating mode of the digital/analog input/output module and hence enable the transmission of analog data. According to the present invention, the testing can be performed with only two pins, which leads to an improvement in test efficiency and a reduction in test cost.

A calibrated test and measurement cable for connecting one or more devices under test and a test and measurement instrument, including a first port structured to electrically connect to a first signal lane, a second port structured to electrically connect to a second signal lane, a third port structured to electrically connect to a test and measurement instrument, and a multiplexer configured to switch between electrically connecting the first port to the third port and connected the second port to the third port. The first and second signal lanes can be included on the same device under test or different devices under test. An input can receive instructions to operate the multiplexer.

An integrated circuit with functional circuitry and testing circuitry, the testing circuitry having a state machine operable in a plurality of different states. The integrated circuit also has a pin for receiving a signal, wherein the state machine is operable to transition between states in response to a change in level of the signal. Circuitry couples the signal of the pin, in a first level, to the state machine in a first time period for causing the state machine to enter a predetermined state, and circuitry maintains the signal in the first level to the state machine in a second time period for maintaining the state machine in the predetermined state. Also during the second time period, circuitry couples data received at the pin to a destination circuit other than the state machine, wherein the destination circuit is operable to perform plural successive scan tests using data from the pin without a power on reset of the functional circuitry.

A circuit couples a test access port (TAP) having a JTAG interface to another port having a serial interface different from the JTAG interface. The circuit includes a forwarding circuit and a timing control circuit. The forward circuit is coupled to couple a test data in (TDI) terminal, a test data out (TDO) terminal, and a test clock (TCK) terminal of the TAP to an input terminal, an output terminal, and a clock terminal of the another port, respectively. The timing control circuit is coupled to drive a select terminal of the another port with a select signal that activates serial data transfer through the serial interface to a device. The timing control circuit delays assertion of the select signal by a configurable time period after assertion of a shift data state of a state machine of the TAP.

The present disclosure describes novel methods and apparatuses for directly accessing JTAG Tap domains that exist in a scan path of many serially connected JTAG Tap domains. Direct scan access to a selected Tap domain by a JTAG controller is achieved using auxiliary digital or analog terminals associated with the Tap domain and connected to the JTAG controller. During direct scan access, the auxiliary digital or analog terminals serve as serial data input and serial data output paths between the selected Tap domain and the JTAG controller.

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.

A system comprises a testing mode register, a set of pins, and a test access port controller. The test access port controller initiates a first testing mode by configuring the set of pins according to a first pin protocol. The test access port controller configures a first pin to receive first test pattern data based on a first convention and configures a second pin to output first test result data based on the first test pattern data. Based on detecting a register command stored in the testing mode register, the test access port controller initiates a second testing mode by configuring the set of pins according to a second pin protocol. The test access port controller configures the first pin to receive a second test pattern data generated based on a second convention and configures the second pin to output a second test result data based on the second test pattern data.

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.

A circuit comprises a plurality of scan chains. The plurality of scan chains comprises bidirectional scan cells. Each of the bidirectional scan cells comprises two serial input-output ports serving as either a serial data input port or a serial data output port based on a control signal. Each of the plurality of scan chains is configured to perform a shift operation in either a first direction or a second direction based on the control signal. The first direction is opposite to the second direction.