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CHAPTER 6 JTAG BOUNDARY SCAN
User’s Manual S14054EJ4V0UM
123
6.6
Initializing TAP Controller
The TAP controller is initialized as follows:
(1) The TAP controller is not initialized by the operation of system input such as system reset.
(2) The TAP controller enters the Test-Logic-Reset controller state at the fifth rising edge of the TCK pin signal
(while the TMS pin signal is held high).
(3) The TAP controller asynchronously enters the Test-Logic-Reset state when the TRST# signal is input.
6.7
Instruction Register
This register is defined as follows (refer to
6.2 Internal Configuration of Boundary Scan Circuit
).
(1) The instruction shifted and input to the instruction register is latched so that it changes only in the Update-IR and
Test-Logic-Reset controller states.
(2) Data is not inverted since it has been serially input to the instruction register until it is serially output.
(3) A fixed binary pattern data “01” (with LSB (Least Significant Bit) being “1”) is loaded to this register cell in the
Capture-IR controller state.
(4) A fixed binary pattern data “01” (with LSB being “1”) is loaded to this register cell in the Test-Logic-Reset
controller state.
(5) While this register is read, data is output from the TDO pin, starting from the LSB to the MSB (Most Significant
Bit), at each falling edge of the TCK pin signal.
The JTAG boundary scan circuit of the
µ
PD98431 can support only the following two instructions depending on
the data set to the instruction register.
•
BYPASS instruction
•
EXTEST instruction
•
SAMPLE/PRELOAD instruction
Instruction Register
D1
D0
Supported Instruction
0
0
EXTEST instruction
0
1
SAMPLE/PRELOAD instruction
1
0
Reserved
1
1
BYPASS instruction