QL7100-6PB516I View Datasheet(PDF) - QuickLogic Corporation

Part Name

Description

MFG CO.

QL7100-6PB516I

Combining Performance, Density, and Embedded RAM

QuickLogic Corporation 

EclipsePlus Family Data Sheet Rev. A

Joint Test Access Group (JTAG)

Figure 4: JTAG Block Diagram

TCK

TMS

TRSTB

TAp Controller

State Machine

(16 States)

Instruction Decode

&

Control Logic

RDI

Mux

Instruction Register

Boundary-Scan Register

(Data Register)

Mux

TDO

Bypass

Register

Internal

Register

I/O Registers

User Defined Data Register

Microprocessors and Application Specific Integrated Circuits (ASICs) pose many design challenges, one

problem being the accessibility of test points. The Joint Test Access Group (JTAG) formed in response to this

challenge, resulting in IEEE standard 1149.1, the Standard Test Access Port and Boundary Scan Architecture.

The JTAG boundary scan test methodology allows complete observation and control of the boundary pins of

a JTAG-compatible device through JTAG software. A Test Access Port (TAP) controller works in concert with

the Instruction Register (IR), which allow users to run three required tests along with several user-defined tests.

JTAG tests allow users to reduce system debug time, reuse test platforms and tools, and reuse subsystem tests

for fuller verification of higher level system elements.

The 1149.1 standard requires the following three tests:

• Extest Instruction. The Extest instruction performs a PCB interconnect test. This test places a device into

an external boundary test mode, selecting the boundary scan register to be connected between the TAP's

Test Data In (TDI) and Test Data Out (TDO) pins. Boundary scan cells are preloaded with test patterns (via

the Sample/Preload Instruction), and input boundary cells capture the input data for analysis.

• Sample/Preload Instruction. This instruction allows a device to remain in its functional mode, while

selecting the boundary scan register to be connected between the TDI and TDO pins. For this test, the

boundary scan register can be accessed via a data scan operation, allowing users to sample the functional

data entering and leaving the device.

• Bypass Instruction. The Bypass instruction allows data to skip a device's boundary scan entirely, so the

data passes through the bypass register. The Bypass instruction allows users to test a device without passing

through other devices. The bypass register is connected between the TDI and TDO pins, allowing serial data

to be transferred through a device without affecting the operation of the device.

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