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12–4
Testability and Diagnostics
29 September 1997 – Subject To Change
Test Interface
TAP Controller
The TAP controller contains a state machine. It interprets IEEE 1149.1 protocols
received on signal tms_h and generates appropriate clocks and control signals for the
testability features under its jurisdiction. The state machine is shown in Figure 12–2.
Figure 12–2 TAP Controller State Machine
Instruction Register
The 5-bit-wide instruction register (IR) supports IEEE 1149.1 mandated public
instructions (EXTEST, SAMPLE, BYPASS, HIGHZ) and a number of optional
instructions for public and private factory use. Table 12–3 summarizes the public
instructions and their functions.
Test Logic
Reset
Run-Test/Idle
Select-IR-Scan
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
Select-DR-Scan
Capture-DR
Shift-DR
Exit1-DR
Pause-DR
Exit2-DR
Update-DR
Capture-IR
Shift-IR
Exit1-IR
Pause-IR
Exit2-IR
Update-IR
Scan Sequence
Scan Sequence
Values
shown
are for
TMS.
MK145508.AI4