
M16C/28 Group
Under development Preliminary specification
Specifications in this manual are tentative and subject to change.
5. Reset
Rev.0.60 2004.02.01
page 29 of N
REJ09B0047-0060Z
5.5.1.1.2. Limitations on WAIT Instruction
If the WAIT instruction is executed when the VC13 bit in the VCR1 register is “1” (VCC
≥ Vdet4) while the
VC27 bit in the VCR2 register is “1” (voltage down detection circuit enable) and the D40 bit in the D4INT
register is “1” (voltage down detection interrupt enable), a voltage down detection interrupt is immediately
generated, causing the microcomputer to exit wait mode.
In systems where the microcomputer enters wait mode when the input voltage at the VCC pin drops below
Vdet4 and exits wait mode when the input voltage rises to Vdet4 or more, make sure the D42 bit is cleared
to "0" when VC13 bit is “0” (VCC < Vdet4) before executing the WAIT instruction.
Figure 5.5.1.1.2.1. Voltage Down Detection Interrupt Generation Block
Voltage down detection interrupt generation circuit
Watchdog
timer interrupt
signal
D42 bit is set to “0”(not detected) by
writing a “0” in a program. VC27 bit
is set to “0” (voltage down detection
circuit disabled), the D42 bit is set to
“0”.
VC27
VC13
Voltage down detection circuit
D4INT clock(the
clock with which it
operates also in
wait mode)
D42
DF1, DF0
1/2
002
012
102
112
1/2
1/8
Non-maskable
interrupt signal
Oscillation stop,
re-oscillation
detection
interrupt signal
Voltage down
detection
interrupt signal
Watchdog timer block
This bit is set to “0”(not detected) by writing a “0” in a program.
Watchdog timer
underflow signal
D43
D41
CM02
WAIT instruction(wait mode)
D40
VCC
VREF
+
-
Noise
rejection
(Rejection wide:200 ns)
Voltage down
detection signal
“H” when VC27 bit= 0
(disabled)
Noise rejection
circuit
Digital
filter
CM10
Figure 5.5.1.1.2.2. Voltage Down Detection Interrupt Generation Circuit Operation Example
Output of the digital filter (Note 2)
D42 bit
Note 1 : D40 is “1”(voltage down detection interrupt enabled)
Note 2 : Output of the digital filter shown in Figure 1.5.8.
Voltage down detection
interrupt signal
No voltage down detection interrupt signals are
generated when the D42 bit is “H”.
sampling
Set to “0” in a
program (not
detected)
VC13 bit
VCC
sampling
Set to “0” in a
program (not
detected)