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CHAPTER 6 JTAG BOUNDARY SCAN
User’s Manual S14054EJ4V0UM
120
6.5
TAP Controller Operation
The TAP controller operates as follows.
The state of the controller is changed by either of (1) and (2) below.
(1) Rising edge of TCK pin signal
(2) TRST# pin input
The TAP controller generates signals that control the operations of the bypass register, boundary scan register,
and instruction register defined by the IEEE1149.1 JTAG Boundary Scan Standard (refer to
Figures 6-4
and
6-5
).
The TDO pin output buffer and the peripheral circuit that selects a register whose contents are to be output to the
TDO pin are controlled as shown in Table 6-1. The TDO pin defined in this table changes at the falling edge of the
TCK pin signal after it has entered each state.
Table 6-1. Operation in Each Controller State
Controller State
Selected Register to Be Driven to TDO Pin
TDO Pin Driver
Test-Logic-Reset
Undefined
High impedance
Run-Test/Idle
Select-DR-Scan
Select-IR-Scan
Capture-IR
Shift-IR
Instruction register
Active
Exit1-IR
Undefined
High impedance
Pause-IR
Exit2-IR
Update-IR
Capture-DR
Shift-DR
Data register (boundary scan register,
bypass register)
Active
Exit1-DR
Undefined
High impedance
Pause-DR
Exit2-DR
Update-DR