H8SXSLASH1663M datasheet(1249/1504 Pages) RENESAS

1249 / 1504 page

Section 26 Boundary Scan

Rev. 2.00 Sep. 24, 2008 Page 1217 of 1468

REJ09B0412-0200

26.5.2

Commands

BYPASS (Instruction Code: B'1111): The BYPASS instruction is an instruction that drives the

bypass register (JTBPR). This instruction shortens the shift path, facilitating the transfer of serial

data to other LSIs on a printed-circuit board at higher speeds. While this instruction is being

executed, the test circuit has no effect on the system circuits.

The bypass register (JTBPR) is connected between the TDI and TDO pins. Bypass operation is

initiated from shift-DR operation. The TDO is at 0 in the first clock cycle in the shift-DR state; in

the subsequent clock cycles, the TDI signal is output on the TDO pin.

EXTEST (Instruction Code: B'0000): The EXTEST instruction is used to test external circuits

when this LSI is installed on the printed circuit board. If this instruction is executed, output pins

are used to output test data (specified by the SAMPLE/PRELOAD instruction) from the boundary

scan register to the print circuit board, and input pins are used to input test result.

SAMPLE/PRELOAD (Instruction Code: B'0100): The SAMPLE/PRELOAD instruction is

used to input data from the LSI internal circuits to the boundary scan register, output data from

scan path, and reload the data to the scan path. While this instruction is executed, input signals are

directly input to the LSI and output signals are also directly output to the external circuits. The LSI

system circuit is not affected by this function.

In SAMPLE operation, the boundary scan register latches the snap shot of data transferred from

input pins to internal circuit or data transferred from internal circuit to output pins. The latched

data is read from the scan path. The scan register latches the snap data at the rising edge of the

TCK in Capture-DR state. The scan register latches snap shot without affecting the LSI normal

operation.

In PRELOAD operation, initial value is written from the scan path to the parallel output latch of

the boundary scan register prior to the EXTEST instruction execution. If the EXTEST is executed

without executing this PRELOAD operation, undefined values are output from the beginning to

the end (transfer to the output latch) of the EXTEST sequence. (In EXTEST instruction, output

parallel latches are always output to the output pins.)

IDCODE (Instruction Code: B'0001): When the IDCODE instruction is selected, IDCODE

the system circuit. INSTR is initialized by the IDCODE instruction in Test-Logic-Reset state of

the TAP controller.

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