A Low-Cost SOC Debug Platform Based on On-Chip Test Architectures

Feng-Xiang Huang

A Scan Cell Design for Scan Based Debugging of an SoC With Multiple Clock Domains A Design-for Debug(DfD) for NoC based SoC Debugging via NoC A Low-Cost SOC Debug Platform Based on On-Chip Test Architecutures Combining Scan and Trace Buffers for Enhancing Real-time Observability in Post Silicon Debugging NIFD: Non-Intrusive FPGA Debugger Debugging FPGA ‘Threads’ for Rapid HW/SW Systems Prototyping

 While the complexity of System-on-a-chip (SoC) design keeps growing rapidly, today the need for an efficient approach to catch design errors at silicon stage has become an urgent issues. In this paper we present a platform for silicon debugging that makes use of an existing test architecture and thus can provide many powerful debug features while requiring very low extra overhead. It supports multi0core debugging for general purpose cores in an SOC chip with the capabilities of on-line tracing, hardware breakpoint insertion and cycle-based stepping. An automatic design tool is also together users can easily control debug operations and examine trace results to efficiently identify the root cause of failures in the silicon.

[3]A Retargetable Embedded In-Circuit Emulation Module for Microprocessors [4]Parameterized Embedded In Circuit Emulator and Its Retargetable Debugging Software for Microprocessor/Microcontroller/D SP Processor [5] Exploiting and I-IP for both Test and Silicon Debug of Microprocessor Cores microprocessor based [12]In-System Silicon Validation and Debug Signal Tracer [6]A Debug Probe for Concurrently Debugging Multiple Embedded Cores and Inter-Core Transactions in NoC Based Systems NoC based [9]An Embedded Processor Based SoC Test Platform [10] Toward Automatic Synthesis of SoC Test Platform Tool [this]

A Low-Cost SOC Debug Platform Based on On-Chip Test Architectures

 Low controllability and observability in post-silicon.

 Even if SoC designers can fetch trace data 。 How to determine in what time intervals bugs occurred to get useful data ?

 A mechanism able to check multi-core data is needed to find inter-core bugs

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They develop a low cost yet very powerful on-chip silicon debug platform.

 Leveraging on-chip resources 。 Embedded CPU, memory, and system bus  Dedicated circuitry 。 Test Access Mechanism(TAM) Controller 。 Test bus 。 IEEE 1149.1 and/or 1500 Wrapped cores 

The advantage of the proposed debug platform

 Testability circuitry has been indispensable  Reusable  Without using expensive external automatic equipment

 Clock Gating • Prevent from signal glitch  Hold Control • Suspend the CUD  TAPC • Convert signals for IEEE1500  TAM Controller (Test Access Mechanism) • Next slide will be presented 4 1 2 3

 The TAM controller is the heart of the debug platform

 AMBA AHB Interface • To communicate with system components through bus   Memory Access Unit TAM as a master, calculates proper addresses to access the embedded memory  Control Unit  TAM as a slave, decode and setup registers to determine which core to be debugged   TMS Generator Convert these TMS signals to control signals for IEEE 1500   BKT Control Unit Detect triggering conditions    Shift Buffer Unit Receive trace responses of CUD’s from TAM OUT port Restore CUDs’ status via TAM IN port

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 Multi-core debugging is needed to identify inter-core bugs  Multiple cores can be connected to different shift buffers and thus can be accessed simultaneously.

 Bugs can be identified by observing the sources and destinations of the signals through the inter-core interconnects.

 It is very difficult to implement without these existing test components.

 Test bus  A set of test buffers  Some required control circuitry

 Successfully implemented this debug platform on the ARM Versatile/PB926EJ-S development system DASTEP

 In comparison with the original test platform     The additional debug area overhead is 36840(um 2 ), which translates to about 7300 gates for the 0.13um technology.

TAM controller is independent of the umber of CUD’s BKT Control Unit added



Silicon debug is a complicated, time-consuming, but inevitable task for today’s SoC designs.

 They present a cost-effective debug solution  Multiple core debugging is also supported  An enhanced DASTEP was developed to help carry out the debug procedure  By reusing existing test components  The area overhead of the extra DfD (design for debug) logic is limited

 The proposed TAMC(Test Access Mechanism Controller) block diagram is useful and worthy to refer.

 How is the meaning of the BKT_cnt?