Joint Test Action Group

architecture, body, electronics, integrated circuit,

standards, testing (JTAG, or "IEEE Standard 1149.1") A

standard specifying how to control and monitor the pins of

compliant devices on a printed circuit board.

Each device has four JTAG control lines. There is a common

reset (TRST) and clock (TCLK). The data line daisy chains

one device's TDO pin to the TDI pin on the next device.

The protocol contains commands to read and set the values of

the pins (and, optionally internal registers) of devices.

This is called "boundary scanning". The protocol makes

board testing easier as signals that are not visible at the

board connector may be read and set.

The protocol also allows the testing of equipment, connected

to the JTAG port, to identify components on the board (by

reading the device identification register) and to control and

monitor the device's outputs.

JTAG is not used during normal operation of a board.

JTAG Technologies B.V. .

Boundary Scan/JTAG Technical Information - Xilinx, Inc..

Java API for Boundary Scan FAQs - Xilinx Inc..

JTAG Boundary-Scan Test Products - Corelis, Inc..

\"Logic analyzers stamping out bugs at the cutting edge\", EDNAccess, 1997-04-10.

IEEE 1149.1 Device Architecture - Boundary-Scan Tutorial fromASSET InterTech, Inc..

\"Application-Specific Integrated Circuits\", Michael JohnSebatian Smith, published Addison-Wesley - Design AutomationCafe.

Software Debug options on ASIC cores - Embedded SystemsProgramming Archive .

Designing for On-Board Programming Using the IEEE 1149.1(JTAG) Access Port - Intel.

Built-In Self-Test Using Boundary Scan by Texas Instruments -EDTN Network.

(1999-11-15)