Chapter 5. Reset - Renesas M16C Series Hardware Manual

R8C/11 Group
5. Reset
There are three types of resets: a hardware reset, a software reset, and an watchdog timer reset.
5.1 Hardware Reset
There are three kinds of hardware reset: hardware reset 1, hardware reset 2, and power-on reset.
After reset, the low-speed on-chip oscillator clock divided by 8 is automatically selected for the
CPU.
5.1.1 Hardware Reset 1
A reset is applied using the RESET pin. When an "L" signal is applied to the RESET pin while
the power supply voltage is within the recommended operating condition, the pins are initial-
ized (see Table 5.1 "Pin Status When RESET Pin Level is 'L'"). When the input level at the
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RESET pin is released from "L" to "H", the CPU and SFR are initialized, and the program is
executed starting from the address indicated by the reset vector. Figure 5.1 shows the CPU
register status after reset and figure 5.2 shows the reset sequence. The internal RAM is not
initialized. If the RESET pin is pulled "L" while writing to the internal RAM, the internal RAM
becomes indeterminate.
Figures 5.3 to 5.4 show the reset circuit example using the hardware reset 1. Refer to Chapter
4, "Special Function Register (SFR)" for the status of SFR after reset.
• When the power supply is stable
(1) Apply an "L" signal to the RESET pin.
(2) Wait for 500 µs (1/f
(3) Apply an "H" signal to the RESET pin.
• Power on
(1) Apply an "L" signal to the RESET pin.
(2) Let the power supply voltage increase until it meets the recommended operating condi-
tion.
(3) Wait td(P-R) or more until the internal power supply stabilizes.
(4) Wait for 500 µs (1/f
(5) Apply an "H" signal to the RESET pin.
Table 5.1 Pin Status When RESET Pin Level is "L"
Pin name
P0
P1
P3 to P3 , P3
0 3 7
P4 P4
5 to 7
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
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20).
RING-S
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20).
RING-S
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Status
Input port
Input port
Input port
Input port
page 14 of 204
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5.1 Hardware Reset
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