IEEE1149.1

Definition and Meaning of JTAG Interface Pins

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Definition and Meaning of JTAG Interface Pins

JTAG has 10-pin, 14-pin, and 20-pin configurations. Although the number of pins and their arrangement differ, some pins are the same across these configurations. The definitions of each pin are as follows. 1. Pin Definitions Test Clock Input (TCK) —– Required 1 TCK is mandated in the IEEE1149.1 standard. TCK provides an independent, basic clock … Read more

Learning JTAG Standard (IEEE1149.1) – Part 2

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Learning JTAG Standard (IEEE1149.1) - Part 2

TAP controller The TAP controller is a finite state machine that transitions states based on the TMS signal at the rising edge of TCK, generating control signals to operate the JTAG circuit. The state transition diagram of the TAP controller is shown below: Each state is described as follows: Test-Logic-Reset: The test logic is disabled, … Read more