7721 datasheet(65/577 Pages) RENESAS

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RESET

7721 Group User’s Manual

4–2

4.1 Hardware reset

When the power source voltage satisfies the microcomputer’s recommended operating conditions, the

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microcomputer is reset by supplying “L” level to the RESET pin. This is called a hardware reset. Figure 4.1.1

shows an example of hardware reset timing.

4.1 Hardware reset

Fig. 4.1.1 Example of hardware reset timing

The following explains how the microcomputer operates in periods to above.

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After supplying “L” level to the RESET pin, the microcomputer initializes pins within a period of several

ten ns. (Refer to “Table 4.1.1.”)

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While the RESET pin is “L” level and within a period of 4 to 5 cycles of

φ after the RESET pin goes from

“L” to “H,” the microcomputer initializes the central processing unit (CPU) and SFR area. At this time,

the contents of the internal RAM area become undefined (except when Stop or Wait mode is terminated).

(Refer to “Figures 4.1.3 to 4.1.9.”)

After , the microcomputer performs “Internal processing sequence after reset.” (Refer to “Figure 4.1.10.”)

The microcomputer executes a program beginning with the address set into the reset vector addresses

(FFFE16 and FFFF16).

RESET

Program is executed.

2 µs or more

Internal processing

sequence after

reset

Note: When the clock is stably supplied. (Refer to section “4.1.4 Time supplying “L” level to

RESET pin.”)

4 to 5 cycles of

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