UPD62AMC datasheet(26/62 Pages) NEC

26 / 62 page

µPD62A

Data Sheet U14474EJ1V0DS00

6. RESET PIN

The system reset takes effect by inputting a low level to the RESET pin.

While the RESET pin is at low level, the system clock oscillator is stopped and the XIN and XOUT pins are fixed

to GND.

If the RESET pin is raised from low level to high level, it executes the program from the 0 address after counting

246 to 694 of the system clock (fX).

Figure 6-1. Reset Operation by RESET Input

The RESET pin outputs a low level when the POC circuit (mask option) is in operation.

Caution When connecting a reset IC to the RESET pin, be sure to connect an IC of the N-ch open drain

output type.

Table 6-1. Hardware Statuses After Reset

• RESET Input During Operation

• RESET Input in Standby Mode

Hardware

• Reset by Internal POC Circuit During Operation • Reset by Internal POC Circuit in Standby

• Reset by Other FactorsNote 1

Mode

PC (10 bits)

000H

SP (1 bit)

Data

R0 = DP

000H

memory

R1-RF

Undefined

Previous status retained

Accumulator (A)

Undefined

Status flag (F)

Carry flag (CY)

Timer (10 bits)

000H

Port register

FFH

×FHNote 2

Control register P3

03H

26H

Notes 1. The following resets are available.

• Reset when executing the HALT instruction (when the operand value is illegal or does not satisfy

the precondition)

• Reset when executing the RLZ instruction (when A = 0)

• Reset by stack pointer’s overflow or underflow

2. Refers to the value based on the KI pin status.

In order to prevent malfunction, be sure to input a low level to more than one of pins KI0 to KI3 when

reset is released (when the RESET pin changes from low level to high level, or POC is released due

to supply voltage startup).

Wait

(246 to 694)/fX +

HALT mode

Oscillation

stopped

Operating mode or

standby mode

RESET

0 address start

α : Oscillation growth time

Operating

mode

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