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CHAPTER 6 JTAG BOUNDARY SCAN
User’s Manual S14054EJ4V0UM
124
6.7.1
BYPASS instruction
This instruction is specified by instruction data “11”. This instruction is used to select only the bypass register (to
access between the TDI and TDO pins serially) in the Shift-DR controller state.
While this instruction is selected, the operation of the JTAG boundary scan circuit does not affect the operation of
the
µ
PD98431.
This bypass instruction is selected while the TAP controller is in the Test-Logic-Reset state.
6.7.2
EXTEST instruction
This instruction is specified by instruction data “00”. In the Shift-DR controller state, this instruction is used to
select the boundary scan register of serial access between the TDI and TDO instructions.
•
While this instruction is selected:
The states of all the signals driven from the system output pins are completely defined by the data shifted to the
boundary scan register. In the Update-DR controller state, the states of all the signals are changed only by the
falling edge of the TCK pin signal.
The states of all the signals input from the system input pins are loaded to the boundary scan register at the rising
edge of the TCK pin signal while the TAP controller is in the Capture-DR state.
6.7.3
SAMPLE/PRELOAD instruction
This instruction is specified by instruction data “01”. This instruction is used to implement two functions: SAMPLE
and PRELOAD.