EXTENDED JTAG CONTROLLER AND METHOD FOR FUNCTIONAL RESET USING THE EXTENDED JTAG CONTROLLER

Abstract

An extended joint test action group based controller and a method of use allows easier testing of integrated circuits by reducing the power dissipation of an IC. The extended joint test action group (JTAG) controller tests internal storage elements that form digital units in an integrated circuit (IC) use a design for testing scan infrastructure on the IC, wherein the JTAG controller is extended by an overall reset generator for all digital units of the IC, and a finite state machine controls the overall reset generator. In reset mode the JTAG controller stops the at least one clock module in supplying the digital units that should be reset. It then sets all scan chains in test mode and switches the input multiplexers into reset mode; and then controls the number of shift clock cycles for shifting in the reset value to the flip-flops in the scan chain, respectively.

Claims

1. An extended joint test action group (JTAG) controller for testing internal storage elements that form digital units in an integrated circuit (IC) using a design for testing (DfT) scan infrastructure on the IC, wherein the JTAG controller is extended by an overall reset generator for all digital units of the IC, and wherein a finite state machine controls the overall reset generator.

2. The extended JTAG controller according to claim 1, wherein the overall reset generator comprises an asynchronous reset module for each digital unit of the IC.

3. The extended JTAG controller according to claim 1, wherein the design for testing scan infrastructure comprises scan chains, whereas all scan chains have a same number of flip-flops.

4. The extended JTAG controller according to claim 1, wherein a dummy flip-flop is inserted in a scan chain, if the number of flip-flops in that scan chain is different to the other scan chains.

5. The extended JTAG controller according to claim 1, wherein the JTAG controller is connected over input multiplexers to the scan chains.

6. The extended JTAG controller according to claim 1, wherein the IC comprises at least one clock module for synchronizing the digital units.

7. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 1, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

8. The method for functional reset of digital units of an IC according to claim 7, wherein in design of testing mode the JTAG controller controls the input multiplexer, wherein a default value is routed through the scan chains.

9. The method for functional reset of digital units of an IC according to claim 7, wherein the design of testing mode and the reset mode are performed by the extended JTAG controller as one single hardware component of the IC.

10. The method for functional reset of digital units of an IC according to claim 8, wherein the design of testing mode and the reset mode are performed by the extended JTAG controller as one single hardware component of the IC.

11. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 2, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

12. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 3, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

13. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 4, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

14. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 5, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

15. A method for functional reset of digital units of an IC using the extended joint test action group (JTAG) controller according to claim 6, wherein in reset mode the JTAG controller stops the at least one clock module in supplying the digital units, that should be reset; sets all scan chains in test mode; switches the input multiplexers into reset mode; and controls the number of shift clock cycles for shifting in the reset value to internal storage elements in the scan chain, respectively.

16. The method for functional reset of digital units of an IC according to claim 15, wherein in design of testing mode the JTAG controller controls the input multiplexer, wherein a default value is routed through the scan chains.

17. The method for functional reset of digital units of an IC according to claim 16, wherein the design of testing mode and the reset mode are performed by the extended JTAG controller as one single hardware component of the IC.

18. A method for functional reset of digital units of an IC according to claim 5, wherein in design of testing mode the JTAG controller controls the input multiplexer, wherein a default value is routed through the scan chains.

19. The method for functional reset of digital units of an IC according to claim 18, wherein the design of testing mode and the reset mode are performed by the extended JTAG controller as one single hardware component of the IC.

20. The method for functional reset of digital units of an IC according to claim 13, wherein in design of testing mode the JTAG controller controls the input multiplexer, wherein a default value is routed through the scan chains.

Description

[0029] The appended drawings show

[0030] FIG. 1 A general clock/reset supply of digital units (state-of-the-art);

[0031] FIG. 2 Common design for testing structure in an IC (state-of-the-art);

[0032] FIG. 3 Inventive merged infrastructure for testing and resetting with the extended JTAG controller;

[0033] FIG. 4 Detailed schematic view of the inventive extended JTAG controller inside an IC.

[0034] FIG. 3 shows the inventive extended JTAG controller 1 wherein asynchronous reset modules 6 for every digital unit 2 of the IC 3 are inserted within the JTAG controller 1 in order to provide an overall reset generator 5 for the digital units 2 in the IC 3. Therefore, the power dissipation can be lowered, because all flip-flops 8 of a digital block/unit 2 do not need a dedicated reset/set pin. It is no longer required that all digital units 2 need their own reset module which saves a lot of IO buffers. All these measurements lead to area reduction as well as leakage reduction and the same functionality for ultra-low power ICs can be provided at the same time. The clock reset modules 13 for every digital unit 2 can be simplified to a clock module 11.

[0035] The merging of the design for testing scan infrastructure 4 with the reset generator 13 in the JTAG controller block 1 lower the power dissipation of the IC 3.

[0036] FIG. 4 shows a detailed schematic view of the inventive JTAG controller 1 inside an IC 3. With the reuse of a common JTAG controller for design for testing tasks as well as for functional resetting of digital units 2 it is possible to lower the power dissipation by reducing the number of IO buffers in the IC 3.

[0037] The merged joint test action group (JTAG) design for testing/resetting controller fulfils the requirement of the IEEE 1149.1 standard (boundary scan) and IEEE 1500 standard (core wrapper test).

[0038] So, the design for test feature set is the same as for a standard DfT control. The design for test feature set in design for test mode controls the input multiplexers (imux's), whereas the default value of the input multiplexer (imux) is routed through the scan chain input. This means, the mux is set in default for design for test (DfT) operation and not for the reset operation. In reset generation mode the selected scan chain is connected to the controller which controls the according input multiplex (imux). This is done by the finite state machine.

[0039] The finite state machine takes over the control of the reset function of the circuit. The sequence of the finite state machine involves switching the input multiplexers (imux) and shifting the reset values through all scan chains. Hence, the finite state machine implicitly controls the number of clock cycles that are needed for the test scan. All scan chains are used simultaneously. At the end of the sequence, the combined JTAG/Reset controller goes into IDLE mode, which saves power. The same sequence can also be executed step by step via JTAG's OP codes from an external JTAG controller.

[0040] For realizing the new extended JTAG controller and method for functional reset using the extended JTAG controller new JTAG op codes for debug mode, input multiplexer control, shift value and shift control of the clock network is needed.

LIST OF REFERENCE SIGNS

[0041] 1 extended joint action group (JTAG) controller [0042] 2 digital unit [0043] 3 integrated circuit (IC) [0044] 4 design for testing infrastructure [0045] 5 overall reset generator [0046] 6 asynchronous reset module [0047] 7 scan chain [0048] 8 flip-flop [0049] 9 dummy flip-flop [0050] 10 input multiplexer [0051] 11 clock module [0052] 12 joint action group (JTAG) controller [0053] 13 combined clock/reset module