M16C65 Datasheet, PDF (108/829 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/60

Under development
M16C/65 Group
Preliminary Specification
This is a preliminary specification and is subject to change.
6. Resets
6.4.10 Cold Start-Up/Warm Start-Up Discrimination
The cold start-up/warm start-up discrimination detects whether or not voltage applied to the VCC1 pin
drops to the RAM hold voltage or below. The reference voltage is Vdet0. Therefore, the voltage monitor
0 reset is used for cold start-up/warm start-up discrimination. Follow Table 7.6 “Steps to Set Voltage
Monitor 0 Reset Related Bits” to set the bits related to the voltage monitor 0 reset.
The CWR bit in the RSTFR register is 0 (cold start-up) when power is turned on. The CWR bit also
becomes 0 after power-on reset or voltage monitor 0 reset. The CWR bit becomes 1 (warm start-up) by
writing 1 by a program and remains unchanged at hardware reset, voltage monitor 1 reset, voltage
monitor 2 reset, oscillation stop detection reset, watchdog timer reset, or software reset.
In the cold start-up/warm start-up discrimination, the Vdet0 level can be selected by setting the
VDSEL1 bit in the OFS1 address.
• When power-on reset or voltage monitor 0 reset is used
Set the VDSEL1 bit to 0 (Vdet0 = 2.85 V (Vdet0_2)).
• When neither power-on reset nor voltage monitor 0 reset is used as the user system
Set the VDSEL1 bit to 1 (Vdet0 = 1.90 V (Vdet0_0)). In this case, voltage monitor 0 reset and its
cancellation are based on Vdet0_0. Therefore, execute hardware reset after the cancellation of
voltage monitor 0 reset.
Figure 6.6 shows the Cold Start-Up/Warm Start-Up Discrimination Example.
5V
VCC1
Vdet0
0V
CWR bit
Voltage monitor 0 reset
Set to 1 by
a program
Set to 1 by
a program
The above diagram shows an instance in which the digital filter is not used.
Figure 6.6 Cold Start-Up/Warm Start-Up Discrimination Example
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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