H8SSLASH2218 datasheet(501/750 Pages) RENESAS

501 / 750 page

Section 13 Boundary Scan Function

Rev.6.00 Jun. 03, 2008 Page 453 of 698

REJ09B0074-0600

EXTEST: The EXTEST instruction is used to test external circuits when this LSI is installed on

the print 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 results.

SAMPLE/PRELOAD: 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 instruction.

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 RELOAD 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.)

CLAMP: When the CLAMP instruction is selected output pins output the boundary scan register

value which was specified by the SAMPLE/PRELOAD instruction in advance. While the CLAMP

instruction is selected, the status of boundary scan register is maintained regardless of the TAP

controller state. BYPASS is connected between TDI and TDO, the same operation as BYPASS

instruction can be achieved.

HIGHZ: When the HIGHZ instruction is selected, all outputs enter high-impedance state. While

this instruction is selected, the status of boundary scan register is maintained regardless of the TAP

controller state. BYPASS resistor is connected between TDI and TDO, the same operation as

BYPASS instruction can be achieved.

IDCODE: When the IDCODE instruction is selected, IDCODE register value is output to the

TDO in Shift-DR state of TAP controller. In this case, IDCODE register value is output from the

LSB. During this instruction execution, test circuit does not affect the system circuit. INSTR is

initialized by the IDCODE instruction in Test-Logic-Reset state of TAP controller.

BYPASS: The BYPASS instruction is a standard instruction necessary to operate bypass register.

The BYPASS instruction improves the serial data transfer speed by bypassing the scan path.

During this instruction execution, test circuit does not affect the system circuit.

H8S/2218 Scheda tecnica(PDF) 501 Page - Renesas Technology Corp