HD404618 Series
15
Reset
The MCU is reset by inputting a high-level voltage to the RESET pin. At power-on or when stop mode is
cancelled, RESET must be high for at least one t
RC
to enable the oscillator to stabilize.
During operation, RESET must be high for at least two instruction cycles.
I/O pins go to high-impedance at power-on.
Initial values after MCU reset are shown in table 1.
Table 1 Initial Values After MCU Reset
Item
Abbr.
Initial Value Contents
Program counter
(PC)
$0000
Indicates program execution
point from start address of ROM
area
Status flag
(ST)
1
Enables conditional branching
Stack pointer
(SP)
$3FF
Stack level 0
V register (bank register)
(V)
0
Bank 0 (memory)
Interrupt flags/mask Interrupt enable flag
(IE)
0
Inhibits all interrupts
Interrupt request flag
(IF)
0
Indicates there is no interrupt
request
Interrupt mask
(IM)
1
Prevents (masks) interrupt
request
I/O
Port data register
(PDR)
All bits 1
Enables output at level 1
Data control register
(DCR)
All bits 0
Turns output buffer off (to high
impedance)
Port mode register A
(PMRA)
0000
Refer to description of port mode
register A
Port mode register B
(PMRB)
0000
Refer to description of port mode
register B
Timer/
counters, serial
interface
Timer mode register A
(TMA)
0000
Refer to description of timer
mode register A
Timer mode register B
(TMB)
0000
Refer to description of timer
mode register B
Timer mode register C
(TMC)
0000
Refer to description of timer
mode register C
Serial mode register
(SMR)
0000
Refer to description of serial
mode register
Prescaler S
$000
—
Prescaler W
$00
—
Timer counter A
(TCA)
$00
—