SH7059 Datasheet, PDF (649/1042 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

20. High-performance User Debug Interface (H-UDI)
20.5 Boundary Scan
The H-UDI pins can be placed in the boundary scan mode stipulated by IEEE1149.1 by setting a command in SDIR.
20.5.1 Supported Instructions
This LSI supports the three essential instructions defined in IEEE1149.1 (BYPASS, SAMPLE/PRELOAD, and EXTEST)
and optional instructions (CLAMP, HIGHZ, and IDCODE).
BYPASS: The BYPASS instruction is an essential standard instruction that operates the bypass register. This instruction
shortens the shift path to speed up serial data transfer involving other chips on the printed circuit board. While this
instruction is executing, the test circuit has no effect on the system circuits. The instruction code is 1111.
SAMPLE/PRELOAD: The SAMPLE/PRELOAD instruction inputs values from this LSI's internal circuitry to the
boundary scan register, outputs values from the scan path, and loads data onto the scan path. When this instruction is
executing, this LSI's input pin signals are transmitted directly to the internal circuitry, and internal circuit values are
directly output externally from the output pins. This LSI's system circuits are not affected by execution of this instruction.
The instruction code is 0100.
In a SAMPLE operation, a snapshot of a value to be transferred from an input pin to the internal circuitry, or a value to be
transferred from the internal circuitry to an output pin, is latched into the boundary scan register and read from the scan
path. Snapshot latching does not affect normal operation of this LSI.
In a PRELOAD operation, an initial value is set in the parallel output latch of the boundary scan register from the scan
path prior to the EXTEST instruction. Without a PRELOAD operation, when the EXTEST instruction was executed an
undefined value would be output from the output pin until completion of the initial scan sequence (transfer to the output
latch) (with the EXTEST instruction, the parallel output latch value is constantly output to the output pin).
EXTEST: This instruction is provided to test external circuitry when this LSI is mounted on a printed circuit board.
When this instruction is executed, output pins are used to output test data (previously set by the SAMPLE/PRELOAD
instruction) from the boundary scan register to the printed circuit board, and input pins are used to latch test results into the
boundary scan register from the printed circuit board. If testing is carried out by using the EXTEST instruction N times,
the Nth test data is scanned-in when test data (N-1) is scanned out.
Data loaded into the output pin boundary scan register in the Capture-DR state is not used for external circuit testing (it is
replaced by a shift operation).
The instruction code is 0000.
CLAMP: When the CLAMP instruction is enabled, the output pin outputs the value of the boundary scan register that has
been set by the SAMPLE/PRELOAD instruction. While the CLAMP instruction is enabled, the state of the boundary scan
register maintains the previous state regardless of the state of the TAP controller.
A bypass register is connected between TDI and TDO. The related circuit operates in the same way when the BYPASS
instruction is enabled.
The instruction code is 0010.
HIGHZ: When the HIGHZ instruction is enabled, all output pins enter a high-impedance state. While the HIGHZ
instruction is enabled, the state of the boundary scan register maintains the previous state regardless of the state of the TAP
controller.
A bypass register is connected between TDI and TDO. The related circuit operates in the same way when the BYPASS
instruction is enabled.
Rev.3.00 Mar. 12, 2008 Page 559 of 948
REJ09B0177-0300