M32CSLASH8A datasheet(61/372 Pages) RENESAS

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M32C/8A Group

6. Power Supply Voltage Detection Function

Rev.1.00

Jul 15, 2007

Page 44 of 352

REJ09B0385-0100

6.2.1

Usage Notes on Vdet4 Detection Interrupt

When all the conditions below are met, the Vdet4 detection interrupt is generated and the MCU exits wait mode

as soon as the WAIT instruction is executed or exits stop mode as soon as the CM10 bit in the CM1 register is

set to 1 (all clocks stopped).

• the VC27 bit in the VCR2 register is set to 1 (Vdet4 detection function used)

• the D40 bit in the D4INT register is set to 1 (Vdet4 detection interrupt enabled)

• the D41 bit in the D4INT register is set to 1 (Vdet4 detection interrupt is used to exit wait/stop mode)

• the voltage applied to the VCC1 pin is Vdet4 or above (the VC13 bit in the VCR1 register is 1)

Execute the WAIT instruction or set the CM10 bit to 1 (all clocks stopped) while the VC13 bit is 0

(VCC1 < Vdet4), if the MCU is configured to enter wait/stop mode when voltage applied to the VCC1 pin

drops Vdet4 or below and to exit wait/stop mode when the voltage applied rises to Vdet4 or above.

If the Vdet4 detection interrupt has been used to exit wait mode or stop mode, set the D41 bit to 0 and then set it

back to 1 to use the Vdet4 detection interrupt again to exit wait/stop mode.

6.3

Cold Start/Warm Start Determine Function

The WDC5 bit in the WDC register determines whether it is a reset process when power-on (cold start) or a reset

process when the RESET signal is input during MCU running (warm start). Default value of the WDC5 bit is 0

(cold start) when power-on, and the bit is set to 1 (warm start) by writing given values to the WDC register. The

WDC5 bit does not become 0 even if the hardware reset 1, hardware reset2, software reset, or watchdog timer reset

is performed.

Figure 6.7 shows an example of cold start/warm start determine function operation.

Figure 6.7

Cold Start/Warm Start Determine Function Operation

The WDC5 bit remains set

to 1 even if voltage applied

to RESET becomes 0 V.

Program starts running

Pch transistor ON (Approx. 4 V)

CPU comes out of reset

Set to 1 by program

T > 100

μs

5 V

0 V

5 V

0 V

VCC1

WDC5 bit

RESET

Reset sequence (Approx.20

μs@16 MHz)

NOTE:

1. If the time difference between T1 and T2 is greater, it may take longer to set the WDC5 bit to 1.

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