HD404618 Datasheet, PDF (17/91 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404618 Series
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
Timer mode register C (TMC) 0000
Serial mode register (SMR) 0000
Prescaler S
Prescaler W
Timer counter A
(TCA)
$000
$00
$00
Refer to description of timer
mode register B
Refer to description of timer
mode register C
Refer to description of serial
mode register
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