Product data

HD404818 Series
17
Reset
Setting the RESET pin high resets the MCU. At power-on or when cancelling the stop mode for the
oscillator, apply the reset input for at least t
RC
for the oscillator to stabilize. In all other cases, at least two
instruction cycles of reset input are required for the MCU reset.
Table 1 shows the components initialized by MCU reset, and each of its status.
Table 1 Initial Values after MCU Reset
Items Initial Value Contents
Program counter (PC) $0000 Execute program from the top of the ROM
address
Status flag (ST) 1 Enable branching with conditional branch
instructions
Stack pointer (SP) $3FF Stack level is 0
V register (bank register) (V) 0 Bank 0 (memory)
Interrupt
flags/mask
Interrupt enable flag (IE) 0 Inhibit all interrupts
Interrupt request flag (IF) 0 No interrupt request
Interrupt mask (IM) 1 Masks interrupt request
I/O Port data register (PDR) All bits are 1 Enable to transmit high
Data control register (DCR) All bits are 0 Output buffer is off (high impedance)
Port mode register A (PMRA) 0000 See Port Mode Register A section
Port mode register B (PMRB) 0000 See Port Mode Register B section
Timer/counters,
serial interface
Timer mode register A (TMA) 0000 See Timer Mode Register A section
Timer mode register B (TMB) 0000 See Timer Mode Register B section
Timer mode register C (TMC) 0000 See Timer Mode Register C section
Serial mode register (SMR) 0000 See Serial Mode Register section
Prescaler S $000
Prescaler W $00
Timer counter A (TCA) $00
Timer counter B (TCB) $00
Timer counter C (TCC) $00
Timer load register B (TLR) $00
Timer load register C (TCR) $00
Octal counter 000