COPCJ820 datasheet(8/32 Pages) NSC

8 / 32 page

Functional Description (Continued)

If the external or RC Clock option is being used

RAM Contents

UNCHANGED

Timer T1 and A Contents

UNCHANGED

WATCHDOG Timer PrescalerCounter

ALTERED

The external RESET takes priority over the Brown Out Re-

set

Note

If the RESET pin is pulled low while Brown Out occurs (Brown Out

circuit has detected Brown Out condition) the external reset will not

occur until the Brown Out condition is removed External reset has

priority only if VCC is greater than the Brown Out voltage

RC l 5 c Power Supply Rise Time

TLDD11208 – 6

FIGURE 4 Recommended Reset Circuit

WATCHDOG RESET

With WATCHDOG enabled the WATCHDOG logic resets

the device if the user program does not service the WATCH-

DOG timer within the selected service window

The

WATCHDOG reset does not disable the WATCHDOG

Upon WATCHDOG reset

the WATCHDOG Prescaler

Counter are each initialized with FF Hex

The following actions occur upon WATCHDOG reset that

are different from external reset

WDREN

WATCHDOG Reset Enable bit

UNCHANGED

WDUDF

WATCHDOG Underflow bit

UNCHANGED

Additional initialization actions that occur as a result of

WATCHDOG reset are as follows

Port L

TRI-STATE

Port G

TRI-STATE

Port D

HIGH

CLEARED

Ram Contents

UNCHANGED

B X SP

UNCHANGED

PSW CNTRL1 and CNTRL2 (except

WDUDF Bit) Registers

CLEARED

Multi-Input Wakeup Registers

WKEDG WKEN

CLEARED

WKPND

UNKNOWN

Data and Configuration

Registers forLG

CLEARED

WATCHDOG Timer

PrescalarCounter

each loaded with FF

BROWN OUT RESET

The on-board Brown Out protection circuit resets the device

when the operating voltage (VCC) is lower than the Brown

Out voltage The device is held in reset when VCC stays

below the Brown Out Voltage The device will remain in

RESET as long as VCC is below the Brown Out Voltage The

Device will resume execution if VCC rises above the Brown

Out Voltage If a two pin crystalresonator clock option is

selected the Brown Out reset will trigger a 256tc delay This

delay allows the oscillator to stabilize before the device ex-

its the reset state The delay is not used if the clock option is

either RC 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 tc 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 forLG

CLEARED

WATCHDOG Timer

PrescalarCounter 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

The development system will detect the BROWN OUT RESET exter-

nally 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

(VCC) and compares it with the minimum operating voltage

specified The Brown Out circuit is designed to reset the

device if the operating voltage is below the Brown Out volt-

age (between 18V to 42V at b40 Cto a85 C) The Mini-

mum operating voltage for the device is 25V with Brown

Out disabled but with BROWN OUT enabled the device is

guaranteed to operate properly down to minimum Brown

Out voltage (Max frequency 4 MHz) For temperature range

of 0 Cto70 C the Brown Out voltage is expected to be

between 19V to 39V The circuit can be enabled or dis-

abled by Brown Out mask option If the device is intended to

operate at lower VCC (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

provided the power supply rise time is slower than 50 ms (0V

to 60V)

Note

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

option selected)

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