COP840C datasheet(12/35 Pages) NSC

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Reset (Continued)

BROWN OUT RESET

The on-board Brown Out protection circuit resets the device

when the operating voltage (V

CC) is lower than the Brown

Out voltage. The device is held in reset when V

CC stays be-

low the Brown Out Voltage. The device will remain in RESET

as long as V

CC is below the Brown Out Voltage. The Device

will resume execution if V

CC rises above the Brown Out Volt-

age. If a two pin crystal/resonator clock option is selected,

the Brown Out reset will trigger a 256tc delay. This delay al-

lows the oscillator to stabilize before the device exits the re-

set state. The delay is not used if the clock option is either

R/C or external clock. The contents of data registers and

RAM are unknown following a Brown Out reset. The external

reset takes priority over Brown Out Reset and will deactivate

the 256 t

c cycles delay if in progress. The Brown Out reset

takes priority over the WATCHDOG reset.

The following actions occur as a result of Brown Out reset:

Port L

TRI-STATE

Port G

TRI-STATE

Port D

HIGH

CLEARED

RAM Contents

RANDOM

B, X, SP

UNKNOWN

PSW, CNTRL1, CNTRL2

and WDREG Registers

CLEARED

Multi-Input Wakeup Registers

WKEDG, WKEN

CLEARED

WKPND

UNKNOWN

Data and Configuration

Registers forL&G

CLEARED

WATCHDOG Timer

Prescalar/Counter each

loaded with FF

Timer T1 and Accumulator

Unknown data after

coming out of the HALT

(through Brown Out

Reset) with any Clock

option

Note 8: The development system will detect the BROWN OUT RESET ex-

ternally and will force the RESET pin low. The Development System does not

emulate the 256tc delay.

Brown Out Detection

An on-board detection circuit monitors the operating voltage

CC) and compares it with the minimum operating voltage

specified. The Brown Out circuit is designed to reset the de-

vice if the operating voltage is below the Brown Out voltage

(between 1.8V to 4.2V at −40˚C to +85˚C). The Minimum op-

erating voltage for the device is 2.5V with Brown Out dis-

abled, but with BROWN OUT enabled the device is guaran-

teed to operate properly down to minimum Brown Out

voltage (Max frequency 4 MHz), For temperature range of

0˚C to 70˚C the Brown Out voltage is expected to be be-

tween 1.9V to 3.9V. The circuit can be enabled or disabled

by Brown Out mask option. If the device is intended to oper-

ate at lower V

CC (lower than Brown Out voltage VBO max),

the Brown Out circuit should be disabled by the mask option.

The Brown Out circuit may be used as a power-up reset pro-

vided the power supply rise time is slower than 50 µs (0V to

6.0V). Brown Out should not be used at frequencies over 4

MHz (COP840CJ).

Note: Brown Out Circuit is active in HALT mode (with the Brown Out mask

option selected).

Oscillator Circuits

EXTERNAL OSCILLATOR

CKI can be driven by an external clock signal provided it

meets the specified duty cycle, rise and fall times, and input

levels. G7/CKO is available as a general purpose input G7

and/or Halt control.

CRYSTAL OSCILLATOR

By selecting G7/CKO as a clock output, CKI and G7/CKO

can be connected to create a crystal controlled oscillator.

Table 1 shows the component values required for various

standard crystal values.

R/C OSCILLATOR (COP820CJ)

For COP820CJ, selecting CKI as a single pin oscillator, CKI

can make a R/C oscillator. G7/CKO is available as a general

purpose input and/or HALT control.

Table 2 shows variation

in the oscillator frequencies as functions of the component

(R and C) values.

TABLE 1. Crystal Oscillator Configuration

CKI Freq.

Conditions

Ω)(MΩ)

(pF)

(MHz)

30–36

CC =5V

30–36

CC =5V

5.6

100/200

100–156

0.455

CC =5V

DS011208-7

FIGURE 5. Clock Oscillator Configurations

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