Automatic connecting system for JTAG chain and implementing method thereof

Abstract

The invention discloses a JTAG chain self-connection system, which comprises the following parts: JTAG controller, at least one JTAG interfaces, at least one JTAG device, CPU, logical control unit and self-connection to control JTAG chain, wherein the TDI pin of JTAG device and TDO pin of JTAG interface connect the input and output end of logical control unit separately; both TCK pin and TMS pin of JTAG interface connect the corresponding pins of JTAG device; the control signal switches the input and output end of logical control unit by CPU through control interface.

Description

technical field [0001] The invention relates to joint test action group (JTAG, Joint Test Action Group) connection technology, especially a JTAG chain automatic connection system and its realization method. Background technique [0002] As circuit technology enters the era of very large-scale integration (VLSI), the high complexity of VLSI circuits and multilayer printed boards, surface mount (SMT), wafer-scale integration (WSI) and multi-chip module (MCM) Due to the application of these technologies, the physical accessibility of circuit nodes is gradually weakening or even disappearing, the testability of circuits and systems has dropped sharply, and the proportion of test overhead in the total overhead of circuits and systems has continued to rise. Conventional testing methods are facing challenges. With increasing testing difficulties. Only by improving the testability of the circuit can the test problem of the circuit be simplified and finally solved. Therefore, peopl...

AI Technical Summary

Problems solved by technology

In this method, the JTAG device in the JTAG chain is fixed after the PCB board is made, that is, the scan chain is fixed, so this method has the following problems: if a certain JTAG device in the JTAG chain is temporarily unnecessary or fails, Then the JTAG chain will be disconnected due to the JTAG device and will not work properly

In addition, as the number of devices in the JTAG chain increases, in order to ensure the normal operation of the JTAG chain, it is necessary to add hardware drive circuits to the control signals TCK, TMS, etc., such as using the drive chip 74HC244, which will cause great changes to the PCB board.

This increases a lot of hardware modification work, and affects the reliability of the JTAG chain connection to a certain extent

[0009] From the perspective of the above JTAG chain connection method, there are disadvantages in the prior art, such as large amount of hardware changes, high complexity, poor flexibility and reliability

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