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© 2002 QuickLogic Corporation
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QL4016 QuickRAM Data Sheet Rev I
JTAG
Figure 10: JTAG Block Diagram
Microprocessors and Application Specific Integrated Circuits (ASICs) pose many design
challenges. One of these challenges concerns 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); these 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.
TCK
TMS
TRSTB
RDI
TDO
Instruction Decode
&
Control Logic
TAp Controller
State Machine
(16 States)
Instruction Register
Boundary-Scan Register
(Data Register)
Mux
Bypass
Register
Mux
Internal
Register
I/O Registers
User Defined Data Register
