Browse Prior Art Database

Method for multiple JTAG device chain support

IP.com Disclosure Number: IPCOM000132636D
Publication Date: 2005-Dec-28
Document File: 3 page(s) / 89K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for multiple JTAG device chain support. Benefits include improved functionality.

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Method for multiple JTAG device chain support

Disclosed is a method for multiple JTAG device chain support. Benefits include improved functionality.

Background

              JTAG is an acronym for the Joint Test Action Group of the

Institute

of

Electrical

and Electronics Engineers, Inc. (registered trademark, IEEE). The Standard for Boundary-Scan Test (1990) is IEEE specification 1149.1. It is administered by JTAG Technologies.

               JTAG is a standard serial protocol to provide control and visibility of processors and chipsets during the validation and debug process. JTAG is a key enabling technology during development. The effectiveness and efficiency of the JTAG controller directly impacts the tasks due to the data volume and the requirement for a fast response time.

              The standard addressing method is serial, which is especially burdensome with components that contain multiple test access port (TAP) interfaces, such as an address length that is in the range of hundreds of bits.

 

Description

              The disclosed method is multiple JTAG device chain support. The disclosed method includes a port connection with at least two IEEE 1149.1 JTAG test clock (TCK) signal pins and a single set of the following JTAG signals (see Figure 1):

•             Test mode select (TMS)

•             Test data in (TDI)

•             Test data out (TDO)

•             Test reset TRST

              The JTAG Manager enables the use of multiple TCK signals for selecting independent JTAG device chains with separate TDI and TDO distributions, which typically operate at different frequencies. As a result, the method permits fully independent TAP state management of the two chains with the multiple TCK signals without requiring fully separate ports (see Figure 2).

              The method, while permitted by the...