H8SSLASH2218 datasheet(511/750 Pages) RENESAS

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Section 13 Boundary Scan Function

Rev.6.00 Jun. 03, 2008 Page 463 of 698

REJ09B0074-0600

13.5

Usage Notes

1. When using the boundary scan function, clear

TRST to 0 at power-on and after the t

RESW time

has elapsed set

TRST to 1 and set TCK, TMS, and TDI appropriately. During normal operation

when the boundary scan function is not used, set TCK, TMS, and TDI to Hi-Z, clear

TRST to 0

at power-on, and after the tRESW time has elapsed set TRST to 1 or to Hi-Z. These pins are

pulled up internally, so care must be taken in standby mode because breakthrough current flow

can occur if there is a potential difference between the pin input voltage value when set to 1

and the power supply voltage Vcc.

2. The following must be noted on the power-on reset signal applied to the

TRST pin.

• Reset signal must be applied at power-on.

• TRST must be separated in order not to affect the system operation.

• TRST must be separated from the system circuitry in order not to affect the system

operation.

• System circuitry must also be separated from the TRST in order not to affect TRST

operation as shown in figure 13.4.

Board edge pin

System

reset

TRST

RES

LSI

Power-on

reset circuit

Figure 13.4 Recommended Reset Signal Design

3. TCK clock speed should be slower than system clock frequency.

4. In serial communication, data is input or output from the LSB as shown in figure 13.5.

Boundary scan register

Bit n

Bit n - 1

Bit 1

Bit 0

TDI

TDO

Figure 13.5 Serial Data Input/Output

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