SH7713 datasheet(785/904 Pages) RENESAS

785 / 904 page

Section 22 User Debugging Interface (H-UDI)

Rev.1.50 Aug. 30, 2006 Page 745 of 860

REJ09B0288-0150

22.5

Boundary Scan

A command can be set in SDIR by the H-UDI to place the H-UDI pins in the boundary scan mode

stipulated by JTAG.

22.5.1

Supported Instructions

This LSI supports the three essential instructions defined in the JTAG standard (BYPASS,

SAMPLE/PRELOAD, and EXTEST) and three option instructions (IDCODE, CLAMP, and

HIGHZ).

BYPASS: The BYPASS instruction is an essential standard instruction that operates the bypass

chips on the printed circuit board. While this instruction is executing, the test circuit has no effect

on the system circuits. The upper four bits of the instruction code are B'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 upper

four bits of the instruction code are 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 is performed in

synchronization with the rise of TCK in the Capture-DR state. 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

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 the 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.

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