M34512M2 Datasheet, PDF (38/80 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

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(1) Power-on reset
Reset can be performed automatically at power on (power-on re-
set) by connecting resistors, a diode, and a capacitor to RESET
pin. Connect RESET pin and the external circuit at the shortest dis-
tance.
VDD
MITSUBISHI MICROCOMPUTERS
4512 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
VDD
RESET pin voltage
RESET pin
(Note)
Internal reset signal
Watchdog timer output
WEF
Reset state
Internal reset signal
Note:
This symbol represents a parasitic diode.
Applied potential to RESET pin must be VDD or less.
Power-on
Reset released
Fig. 32 Power-on reset circuit example
(2) Internal state at reset
Table 17 shows port state at reset, and Figure 33 shows internal
state at reset (they are the same after system is released from re-
set). The contents of timers, registers, flags and RAM except
shown in Figure 33 are undefined, so set the initial value to them.
Table 17 Port state at reset
Name
D0–D7
P00–P03
P10–P13
P20/SCK, P21/SOUT, P22/SIN
Notes 1: Output latch is set to “1.”
2: Pull-up transistor is turned OFF.
Function
D0–D7
P00–P03
P10–P13
P20–P22
High impedance (Note 1)
State
High impedance (Notes 1, 2)
High impedance
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