M16CSLASH29 datasheet(59/499 Pages) RENESAS

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5. Resets

page 35

5. Resets

Hardware reset 1, brown-out detection reset (hardware reset 2), software reset, watchdog timer reset, and

oscillation stop detection reset are implemented to reset the MCU.

5.1 Hardware Reset

Hardware reset 1 and brown-out detection reset are available as the hardware reset.

5.1.1 Hardware Reset 1

____________

Pins, CPU, and SFRs are reset by using the RESET pin. When a low-level (“L”) signal is applied to the

____________

RESET pin while the supply voltage meets the recommended operating condition, pins, CPU, and SFRs

____________

are reset (see Table 5.1 Pin Status When RESET Pin Level is “L”). The oscillation circuit is also reset and

the on-chip oscillator starts oscillating as the CPU clock. CPU and SFRs re reset when the signal applied

____________

to the RESET pin changes from “L” to high (“H”). The MCU executes a program beginning with the

address indicated by the reset vector. The internal RAM is not reset. When an “L” signal is applied to the

____________

RESET pin while writing data to the internal RAM, the content of internal RAM is undefined.

Figure 5.1

shows an example of the reset circuit. Figure 5.2 shows a reset sequence. Table 5.1 shows

____________

status of the other pins while the RESET pin is held “L”. Figure 5.3 shows CPU register states after reset.

Refer to 4. Special Function Register (SFR) about SFR states after reset.

1. Reset on a stable supply voltage

____________

(1) Apply an “L” signal to the RESET pin

(2) Wait

td(ROC) or more

____________

(3) Apply an “H” signal to the RESET pin

2. Power-on reset

____________

(1) Apply an “L” signal to the RESET pin

(2) Increase the supply voltage until it meets the the recommended performance condition

(3) Wait for

td(P-R) or more to allow the internal power supply to stabilize

(4) Wait

td(ROC) or more

____________

(5) Apply an “H” signal to the RESET pin

5.1.2 Brown-Out Detection Reset (Hardware Reset 2)

Note

Brown-out detection reset in the M16C/29 Group, T-ver. and V-ver. cannot be used.

Pins, CPU, and SFR are reset by using the on-chip voltage detection circuit, which monitors the voltage

applied to VCC pin.

When the VC26 bit in the VCR2 register is set to 1 (reset level detection circuit enabled), pins, CPU, and

SFR are reset as soon as the voltage applied to the VCC pin drops to Vdet3 or below.

Then, pins, CPU, and SFR are reset as soon as the voltage applied to the VCC pin reaches Vdet3r or

above. The MCU executes the program in an address determined by the reset vector.

The MCU executes the program after detecting Vdet3r and waiting

td(S-R) ms. The same pins and

registers are reset by the hardware reset 1 and brown-out detection reset, and are also placed in the

same reset state.

The MCU cannot exit stop mode by brown-out detection reset.

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