1

Podstawy techniki

mikroprocesorowej

ETEW006

Redukcja mocy

EMC

Niezawodność działania programów

Andrzej Stępień

Katedra Metrologii Elektronicznej i Fotonicznej

Silicon Labs C8051F50x

Supply Voltage 1.8 to 5.25 V

typical operating current: 18 mA @ 50 MHz; 20

µ

A @ 32 kHz

typical stop mode current: 3

µ

A

Digital Peripherals

−

All I/O Ports 5 V tolerant with high sink
current

−

CAN 2.0 Controller – no crystal required

−

LIN 2.0 Controller (Master and Slave
capable); no crystal required

−

Hardware enhanced UART, SMBus™, and
enhanced SPI™ serial ports

Clock Sources

−

Internal 24 MHz with ±0.5% accuracy

for CAN and master LIN operation

−

External oscillator: Crystal, RC, C, or clock (1 or 2 pin modes)

−

switch between clock sources on-the-fly

; useful in power saving modes

Temperature Range: –40 to +125 °C

TI MSP430F2xxx / MSP430F54xx

Low Supply Voltage Range 1.8 V to 3.6 V

Ultralow Power Consumption (MSP430F54xx):

−

Active Mode (AM): 165

µ

A/MHz at 8 MHz

−

Standby Mode (LPM3 RTC Mode): 2.60

µ

A

−

Off Mode (LPM4 RAM Retention): 1.69

µ

A

−

Shutdown Mode (LPM5): 0.1

µ

A

Five Power-Saving Modes

Ultrafast Wake-Up From Standby Mode in Less Than 1

µ

s

(MSP430F2xxx)

Basic Clock Module Configurations

(MSP430F2xxx):

−

Internal Frequencies up to 16 MHz With Four
Calibrated Frequencies to ±1%

−

Internal Very Low Power LF Oscillator

−

32-kHz Crystal

−

External Digital Clock Source

How to
power an
MCU

Power Consumption

static

(P

s

) – in the datasheet:

•

I

CC

•

∆∆∆∆

I

CC

dynamic

power consumption (P

d

) – usually forms the bulk

of power consumption:

•

transient power consumption

(P

t

)

•

capacitive load power consumption

(P

L

)

CMOS Power Consumption and Cpd Calculation.

Texas Instruments, SCAA035B, June 1997

Static Power Consumption

I

CC

– supply current

P

S

= V

CC

∗

I

CC

where: V

CC

= supply voltage

I

CC

= current into a device

(sum of leakage currents)

∆∆∆∆

I

CC

– extra supply current for every input that is at a voltage other

than 0 or 5V (when the input levels are not driven all the way to
the rail, causing the input transistors to not switch off completely)

Dynamic Power Consumption

transient power consumption

(P

t

):

P

T

= C

pd

∗

V

CC

2

∗

f

I

∗

N

SW

where: C

pd

= dynamic power-dissipation capacitance

V

CC

= supply voltage

f

I

= input signal frequency

N

SW

= number of bits switching

capacitive load power consumption

(P

L

):

P

L

= C

L

∗

V

CC

2

∗

f

O

∗

N

SW

(C

L

is the load per output)

where: V

CC

= supply voltage

f

O

= output signal frequency

C

L

= external (load) capacitance

N

SW

= total number of outputs switching

2

Power Consumption With a Single

Output Switching for TI’s ’245

Figure 8. Power Consumption With a Single Output Switching for TI’s ’245

I

C

C

[m

A

]

Frequency [MHz]

Power

Consumption

in Golf

(das Auto)

Figure 4 Reducing the

average current draw
has different impacts
on battery life.

Matt Ruff (Freescale Semiconductor)
Reducing power consumption in
batterypowered applications.
EDN, 2007, may 24, p. 81

Medical Electronics

Steve Kennelly: Reducing Power Consumption in Embedded Medical

Electronics. Medical Electronics Manufacturing, Spring 2007

Small device packages, reduced power consumption

Advanced semiconductors

that

integrate more features on a single

device

have enabled designers to

miniaturize medical devices

and to

extend device lifetimes

by

lowering power consumption

Batteries

are the

principal power

source

in

many low-power

applications

Batteries

that are suitable for

high-current applications

have

lower

capacity

or

greater weight

than a similarly sized high-internal-resistance

battery

MCU

to be able to handle a variety of low-powered designs, it is important that

it

operate

with a

wide range of power supplies

: for instance, when a device

uses

alkaline batteries

,

1.8-V

operation is desirable because the

end voltage

on each

cell is 0.9 V

and the

application typically employs two cells

Power Reduction Methods

in MCU

Some

MCU families

now commercially

available

provide special features for

power management

; these generally involve controlling power consumption

by peripherals, letting the

MCU sleep periodically

, or

manipulating

oscillator start-up

Controlling Power to Peripherals

– a cardinal principle of power

management in portable embedded systems is to enable the

MCU to control

the

power used by both internal and external peripherals

; for example, a

brownout-reset feature is not needed in battery-powered applications. A
designer thus can save power by disabling it

MCU Sleep Modes

– put the

MCU to sleep occasionally

, at times when the

system's demand for the controller's resources is low; then, to perform useful
work, the sleeping MCU is awakened, either through an interrupt or when a set
period on a watchdog timer has expired – longer the MCU can be allowed to
sleep, the lower the average power consumed by the application will be

Power Reduction Methods

Oscillators

Start-up event

occurs

while

the

MCU is idle

(that is, not executing any code):

−

during the start-up period, as the oscillator stabilizes, the MCU is not doing
any work, yet it continues to consume power

−

oscillator start-up time

usually

is not mentioned

in the MCU's data

sheet, because its

duration

will

vary depending on the crystal

,

loading

capacitors

,

system environment

,

oscillator mode

, and so on

Use a two-speed oscillator start-up

:

−

MCU immediately starts to execute code from a fast-starting secondary
oscillator, such as a RC oscillator

−

when the primary oscillator is ready, it is switched into the circuit to replace
the secondary oscillator

−

such a design is critical for applications in which a device cycles from sleep
to waking and back frequently

Power Reduction Methods

Bidirectional I/O pins

designers should be careful about the signals applied to these pins so
that the amount of power consumed can be minimized

if a port

pin

is

unused

, the designer can leave it unconnected but

configured as

an output pin driving to either state,

high

or

low

, or, it can

be

configured

as an

input

with an

external resistor

pulling it to V

DD

(the

supply voltage) or V

SS

(the ground)

when the port pin is

configured

as an

input

, only the pin

input leakage

current

will be drawn through it – current flow would be the same if the

pin were connected directly to V

DD

or V

SS

in this way, the pin can be used later, for either input or output, without
extensive hardware changes

3

Power Reduction Methods

Peripherals

Figure 1. The I/O

pins

of an MCU can be

used to power

the

EEPROM

and the

sensor

in this data-recorder application

Power

Consumption

Matt Ruff (Freescale Semiconductor): Reducing power consumption

in batterypowered applications. EDN, 2007, may 24, p. 82

RUN MODE

EXTERNAL EVENT TRIGGERS RUN MODE,
FAST START-UP WITH 4-MHz-BUS SELF-CLOCK MODE

COMPARATIVE

POWER

CONSUMP

STOP 1

STANDBY POWERDOWN,
TYPICALLY, 20 nA AT 2V

STOP 2

WITH AVERAGE WAIT TIME/

REAL-TIME CLOCK ENABLED
INTERNAL 2-kHz WAKE-UP

OSCILLATOR ON

RAM AND I/O CONTENTS POWERED,
TYPICALLY, 700 nA AT 2V

RUN MODE

AVERAGE WAIT TIME/RTC TRIGGERS RUN MODE
CHECK WHETHER HIGH-SPEED SERVICE IS
NECESSARY;
IF NOT, GO BACK TO STOP 2 WITH AVERAGE WAIT
TIME ENABLED

RUN MODE

HIGH-SPEED SERVICING IS REQUIRED:
INCREASE BUS SPEED TO 20 MHz WITH
INTERNAL CLOCK GENERATOR
COMPLETE TASK, THEN GO BACK TO
STOP 2 WITH AVERAGE WAIT TIME

STOP 1

DEVICE TIMES OUT, ENTER
STANDBY POWERDOWN,
TYPICALLY 20 nA AT 2V

Fig. 2 The power-

consumption profile
for stop and run
modes includes a
periodic wake-up

Active versus Sleep Mode

(AVR MCU) (1/2)

Arne Martin Holberg, Asmund Saetre: Innovative Techniques for Extremely Low
Power Consumption with 8-bit Microcontrollers. White Paper, Atmel Co. 2006

In many applications, the

processor does not run continuously and peripherals

may be idle much of the time

. The overall power consumption can be lowered by

taking advantage of various “sleep” modes available on virtually all processors. The
most common sleep modes are Power Down (PWD), Power Save (PS) and Idle.

In Power Down mode everything is shut down, including the clock source.

In Power

Save mode everything is turned off except a 32 kHz clock running from a crystal
to keep track of time.

Idle mode is a shallow sleep mode where only parts of the

device are shut down but the main parts of the microcontroller are running.

The advantage of having multiple sleep modes is the flexibility it provides to shut down
any part of the microcontroller that is not absolutely necessary to the function at hand.
The amount of power that can be saved depends on the mode being using. For
example with a

1.8V supply voltage

operating at

1 MHz and 25ºC

, Atmel’s

ATmega165P AVR

controller consumes

340

µµµµ

A in Active mode

,

150

µµµµ

A

in

Idle

mode

,

0.65

µµµµ

A in Power Save

mode and a scant

0.1

µµµµ

A in Power Down mode

.

Active versus Sleep Mode

(AVR MCU) (2/2)

A. M. Holberg, A. Saetre: Innovative Techniques for Extremely Low Power Consumption

with 8-bit Microcontrollers. White Paper, Atmel Co. 2006

Time

Sleep I

CC

Active I

CC

Current

consumption

10% Duty Cycle

Average current

Figure 1: Power budget

Low-Power Applications

Principles

Most important factor for

reducing power consumption

is

using

the clock

system with both a

real-time clock function and all interrupts active

(MSP430Xxxx: 32-kHz watch crystal is used for the ACLK and the CPU is
clocked from the DCO (normally off) which has a 6-

µ

s wake-up)

Use interrupts to wake the processor

and control program flow

Peripherals should be switched on only when needed

Use low-power integrated peripheral modules

in place of software driven

functions (MSP320Xxxx: for example Timer_A and Timer_B can automatically
generate PWM and capture external timing, with no CPU resources)

Calculated branching and fast table look-ups

should be used in place of

flag polling and long software calculations

Avoid frequent subroutine and function calls due to overhead

For

longer software routines

,

single-cycle CPU registers

should be used

Power Saving Modes

Active Mode

– CPU is Active and all Modules (Peripherals) are Active

Slow–Down Mode

– slows down all parts of the controller, the CPU and all

peripherals; Slowing down the frequency significantly reduces power
consumption. The slow down mode can be combined with the idle mode

Idle Mode

– CPU is gated off from the oscillator, all peripherals are still

provided with the clock and are able to work; Idle Mode is entered by software
and can be left by an interrupt or reset

Atmel: Idle mode is a shallow

sleep mode

where only parts of the device are

shut down but the main parts of the microcontroller are running

Wait Mode

– CPU operation is stopped, oscillators remains active (Renesas)

Standby Mode

– Low-power Mode 3 in MSP430 (LPM3), disabled: CPU,

MCLK, SMCLK, DCO’s dc-generator is disabled; ACLK remains active

Power Down Mode / Stop Mode / Halt Mode

– (Hardware or Software)

operation of the MCU is completely stopped and the oscillator is turned off;
this mode is used to save the contents of the internal RAM with a very low
standby current

DVS

– Dynamic Voltage Scaling

4

COP8CBR

National Semiconductor

The low speed oscillator is left on in HALT mode, because

the low speed

oscillator draws very little operating current

.

HS Osc off

LS Osc on

HS Osc off

LS Osc on

Idle

Halt

Low

Speed

Mode

32 kHz

HS Osc off

LS Osc on

T0 clked by LS Osc

Idle

HS Osc off

LS Osc on

HS Osc off

LS Osc on

Halt

Halt

HS Osc off

LS Osc on

Idle

Reset

Dual

Clock
Mode

HS Osc on

LS Osc on

T0 clked by LS Osc

HS Osc on

LS Osc off

T0 clked by HS Osc

High

Speed

Mode

MSP430 Low Power Mode

(Texas Instruments)

RST/NMI

NMI Active

WDTIFG=0

POR

PUC

RST/NMI is Reset Pin
WDT is Active

Vcc On

RST/NMI

Reset Active

WDT Active

Time Expired, Overflow

WDTIFG=1

WDT Active

Security Key Violation

All On

Low Power Mode 4

CPU Off, MCLK Off, SMCLK Off

DCO Off, DC Gen Off

ACLK Off

All Off

Low Power Mode 3

CPU Off, MCLK Off, SMCLK Off

DCO Off, DC Gen Off

ACLK On

Icc=1mA

@Vcc=2,2V

Low Power Mode 2

CPU Off, MCLK Off, SMCLK Off

DCO Off,

DC Gen On

ACLK On

Icc=11mA

(@Vcc=2,2V)

Low Power Mode 1

CPU Off, MCLK Off,

SMCLK On

DCO Off,

DC Gen On

ACLK On

Low Power Mode 0

CPU Off, MCLK Off,

SMCLK On

DCO On, DC Gen On

ACLK On

Icc=65mA

@Vcc=2,2V

Icc=225mA

(@Vcc=2,2V)

Active Mode

CPU is Active

Various Modules are Active

Icc=0,1mA

@Vcc=2,2V

P

Cortex-M3

CPU execution is suspended

Peripherals continue running

Main oscillator and all internal clocks except the IRC
are stopped

Flash memory is in standby, ready for immediate use

Same as Deep-Sleep mode except
Flash and IRC are shut down

All clocks including IRC are stopped.
Internal voltage is turned off

Complete system state is lost, only
special registers in the RTC domain are
preserved

Wake up via reset, external pin, or RTC
Alarm

???

One question system designers may ask themselves is:

“

Why do I need one of these things anyway

?”

There are 3 situations that you must consider when answer-ing this
question:

• what would happen to the microcontroller (or other devices in the

system) if there was noise on the

supply voltage as it powers up

?

• what would happen if there is a

glitch

on the power supply while the

system is running

?

• what does the microcontroller do when the

system power is turned

off

?

V

CC

=5V

Low e nd of ope ra ting ra nge

Mic ro co ntro lle r 'lo s es c o ntro l' he re

Othe r compone nts
in s ys te m
may work down to here

Dan ge r

Zone

Glitc h

in power

s upply

t

t

Gmin

M

a nua l

R

es e t

V

IT

RES ET

Output Undefine d

t

d

t

d

t

d

AN686, Microchip

S LVA056A,
Te xas Ins trum e nts

V

IT+

= 4,59V

V

hys

~1,5V

~0,7 .. 1.1V

V

IT-

= 4,55V

>200ns

200ms

Glitch
in

power
supply

Output Undefined

Brown-Out Detection

LPC213x

UM10120. LPC2131/2/4/6/8 User manual.

Philips Semiconductors, Rev. 02 – 25 July 2006

BOD has 2-stage monitoring

of the voltage on the V

DD

pins:

•

if

V

DD

voltage falls

below 2.9 V

, the Brown-Out Detector (BOD)

asserts an interrupt signal to the Vectored Interrupt Controller
(must be enabled for interrupt)

•

if

V

DD

voltage falls

below 2.6 V

, Reset prevents alteration of the

Flash as operation of the various elements of the chip

•

both

the

2.9 V

and

2.6 V

thresholds

include some hysteresis

BOD circuit maintains this reset

down below 1 V, at which point the

Power-On Reset circuitry maintains the overall Reset

BOD wakes up MCU

and continues operation, bring LPC213x out of

Power-Down mode

5

DVS

D

ynamic

V

oltage

S

caling:

• dynamiczne przeł

ą

czanie napi

ęć

zasilaj

ą

cych w układach, które nie

pracuj

ą

z pełn

ą

moc

ą

(np. odtwarzacz MP3, internetowe audio, kamera

cyfrowa itp.)

• obni

ż

enie napi

ę

cia zasilania rdzenia (U

CC

), zmniejszenie cz

ę

stotliwo

ś

ci

taktuj

ą

cej (f

CLK

) w mikroprocesorach, procesorach sygnałowych (DSP)

• pobór energii proporcjonalny do (U

CC

)

2

∗

F

CLK

, zmiana cz

ę

stotliwo

ś

ci

taktuj

ą

cej

• wydłu

ż

enie czasu

ż

ycia baterii o ok. 15-25% przy oszcz

ę

dnym

gospodarowaniu energi

ą

• wła

ś

ciwe zaprojektowanie struktury mikroprocesora, DSP steruj

ą

cej

stabilizatorem napi

ę

cia

Power Management Mode (PMM)

(1/3)

Kevin Self - Microcontrollers Applications
Engineer, Dallas Semiconductor Corporation

PMM1

XTAL/64

PMM2

XTAL/1024

software

Active Mode

Cristal Oscillator XTAL/4

/Ring Oscillator

Idle Mode

(only CPU OFF)

Stop Mode

XTAL OFF

(All OFF)

hardware

Stop Mode

All OFF +

Cristal Ampl. OFF

External Interrupt or RESET

I

CC

Current

XTAL/4

1 2

4

6

8

10 12 14

16 18

20

5

10

15

20

Icc [mA]

Frequency [MHz]

22

24 26

28 30

(active mode
full speed)

25

30

Type of mode:

35

Idle

XTAL/64

(PMM1 with NOP)

XTAL/1024

(PMM2 with NOP)

Stop Mode

(1 mA)

(backward software
compatibility)

DS80C320
(4 clocks - performance 2,5x)

Exit from Stop Mode

Cristal

Oscillator

Power

µ

C operating

µ

C enters

Stop Mode

Ext. Interrupt

Clock starts

Clock

stabile

µ

C enters

Stop Mode

µ

C operating

4 .. 10 ms

Power saved

RC

Oscillator

Cristal

Oscillator

Power

µ

C operating

µ

C enters

Stop Mode

Ext. Interrupt

Clock starts

µ

C enters

Stop Mode

µ

C operating

Power .vs. Clock Frequency

Burst Mode Operation
Energy consumed vs. processor speed for a 500 machine cycle task,
active mode

Clock

Machine

Total

Current

Frequency

Cycle

Time

I

CC

-Time

Period

Product

10 MHz

400 ns

200 ms

12,41 mA

248 mAs

30 MHz

133 ns

66,5 ms

34,66 mA

230 mAs (

–6%

)

Wewnętrzne generatory

MSP430x1xx

LFXT1CLK

- Low/high-frequency oscillator:

• low-frequency 32,768-Hz watch crystals
•standard crystals, resonators
•external clock in the 450k .. 8MHz range

XT2CLK

- Optional high-frequency oscillator:

•standard crystals
•resonators
•external clock in the 450k .. 8MHz range

DCOCLK

- Internal digitally controlled

oscillator (DCO) with RC-type characteristics.

6

Rezonator kwarcowy

(1/2)

L

1

C

1

R

1

C

0

f

S

=

1

2

Π √

L

1

C

1

Układ zast

ę

pczy

rezonatora kwarcowego

bez obudowy i mocowania

Cz

ę

stotliwo

ść

rezonansu

szeregowego:

Cz

ę

stotliwo

ść

rezonansu

równoległego:

f

a

=

1

2

Π

√

1

L

1

C

1

1

L

1

C

0

+

= f

S

√

C

1

C

0

+

1

B. Gniewi

ń

ska, C. Klimek: Rezonatory i generatory kwarcowe. WKiŁ, Warszawa 1980

Reaktancja

X

L

X

C

f

f

S

f

a

Rezonator kwarcowy

(2/3)

L

1

C

1

R

1

C

0

A

B

C

X1

C

X2

C

X

MCU

Cz

ę

stotliwo

ść

rezonansu

równoległego:

f

a

= f

S

√

C

1

C

L

+ C

0

+

1

C

L

= C

X

+

C

X1

C

X2

C

X1

+ C

X2

gdzie:

f

a

- f

S

f

S

< 0,01 .. 0,5 %

HC 49U

HC 49S

HC 49S/SMD

HC 49S

/SMD

TF206

Startup Time

COP8CBR9/COP8CCR9/COP8CDR9. 8-Bit CMOS Flash Microcontroller
with 32k Memory, Virtual EEPROM, 10-Bit A/D and Brownout.
DS101374, April 2002, National Semiconductor

CKI Frequency Startup Time

10 MHz

1 – 10 ms

3.33 MHz

3 – 10 ms

1 MHz

3 – 20 ms

455 kHz

10 – 30 ms

32 kHz

2 – 5 sec (low speed oscillator)

Clay Turner: Use of the TMS320C5x Internal Oscillator With External Crystals or
Ceramic Resonators. SPRA054, October 1995, Texas Instruments

„

Startup time

is dependent on the external components used, but

generally requires at last

100 ms

after power-up for the oscillator to

stabilize. For this reason, a

reset delay

of

150-200 ms

is recommended

following power-up.”

Crystal Oscillator Start-Up

Oscillator Start-Up (4.608 MHz Crystal
from Standard Crystal Corp.)

V

CC

V

CC

X2

X2

C

X1,2

= 30 pF

C

X1,2

= 50 pF

T

S

, ms

TOM WILLIAMSON: Oscillators for
Microcontrollers
APPLICATION NOTE AP-155, June 1983, Intel Corp.

Parametry rezonatorów kwarcowych

Nominal frequency range

f

32.768 kHz

Temperature

storage

T

STG

−

55

°

C to +125

°

C

range

operating

T

OPR

−

40

°

C to +85

°

C

Maximum drive level

GL

1,0

µ

W

MAX

Soldering condition

T

SOL

Twice at under 260

°

C within 10 s

or under 230

°

C within 3 min.

Frequency tolerance (standard)

∆

f/f

±

20ppm or

±

50ppm

(Ta=25

°

C, DL=0.1

µ

W)

Peak temperature (frequency)

θ

T

25

°

C

±

5

°

C

Temperature coefficient (frequency)

α

−

0.04ppm/

°

C

MAX

Load capacitance

C

L

6pF

Series resistance

R

1

50k

Ω

MAX

Motional capacitance

C

1

1.8pF

MAX

Shunt capacitance

C

0

0.9pF

MAX

Insulation resistance

IR

500M

Ω

MIN

Aging

fa

±

3ppm/Y

MAX

(Ta=25

°

C

±

3

°

C, first year)

Shock resistance

S.R.

±

5ppm

MAX

(test with: 3000G x 1/2 sine wave x 3 directions)

Crystal Specifications

Crystal Considerations with
Dallas Real Time Clocks. APP58,
Dallas Semiconductor, 1995

Nominal Freque ncy

Pa ra meter

Load Ca pa cita nce

Symbol

Min

Typ

Ma x

Units

Te mpe rature Turnove r Point

Para bolic Curva ture Cons ta nt

Qua lity Fa ctor

Series Res ista nce

Shunt Capa citance

Capacita nce Ra tio

Drive Le ve l

32,768

kHz

6

pF

25

30

20

C

ppm/ C

0,042

Q

70.000

40.000

45

k

Ω

pF

1,1

1,8

430

600

1

µ

W

C

L

F

0

T

0

k

R1

C

0

D

L

C / C

0

1

o

o

Daiwa DS-26S Crystal

Specifications

0

-20
-40

-80

-60

-100
-120

-160

-140

-180

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

Temperature [

°

C]

Delta

frequency

[ppm]

DS1485

(25

°

C):

±

30 seconds / month (C

L

= 6 pF)

±

4 minutes / month (C

L

= 12 pF)

7

PCB - Crystal Oscillator

Peter Mariutti: Crystal Oscillator of the C500 and C166 Microcontroller Families.
ApNote AP242005, Infineon Technologies, 1999

Quartz Crystals

&

Ceramic Resonators

Peter Mariutti: Ceramic Resonator Oscillators and the C500 and C166
Microcontroller Families. ApNote AP242401, Infineon Technologies, 1999

Principal technical Differences between Quartz Crystals and Ceramic
Resonators

Ceramic Resonator

Quartz Crystal

Price Factor (depends on quality)

1

2

Mechanical Shock Resistance

very good

good

Integrated Caps available

yes

no

Aging (for 10 years at room temperature) ± 3000 ppm

± 10 ppm

Initial Frequency Tolerance

± 2000 ... 5000 ppm

± 20 ppm

Temperature Characteristics

± 20 ... 50 ppm/°C

± 0. 5 ppm/°C

Load Capacitance Characteristics

± 100 ... 350 ppm/pF

± 15 ppm/pF

Oscillation Rise Time

0.01 ... 0.5 msec

1 ... 10 msec

Quality Factor (Qm)

100 ... 5 000

10 000 ... 500 000

Internal RC Oscillator

AVR051: Set-up and Use the External RC Oscillator.
Application Note, Atmel Corporation 2002

f

≈

1

3 R C

Short start-up time of RC oscillator:

max. 4 µs + 10 clock cycles

Frequency and power consumption for C=22pF

(1)

/

C=100pF

(2)

, simulated values

Resistor Value (k

Ω

) Frequency (MHz) Typical Consumption Current (mA)

1.2

11.9 /

4.54

1.0 /

0.57

2.2

7.36 /

2.32

1.0 /

0.18

3.9

4.40 /

1,41

0.57 /

0.18

8.2

1.98

0.18

18.0

0.99

0.18

(1)

C = 22 pF, and 12 pF stray capacitance (package, pad, pin, and PCB)

(2)

C = 100 pF, and 12 pF stray capacitance (package, pad, pin, and PCB), 5V

ATmega8(L)

Internal Calibrated RC

Oscillator Frequency vs.
Operating Voltage
(the devices are calibrated to
8 MHz at V

CC

= 5V, T=25

°

C)

Internal Calibrated RC

Oscillator Frequency vs.
Temperature
(the devices are calibrated
to 8 MHz at V

CC

= 5V,

T=25

°

C)

20

°°°°

C

5V

3V

LPC247x

Internal RC osc. temperature characteristics

Ceramic Resonator Start-Up

Oscillator Start-Up
(3.58 MHz Ceramic Resonator
from NTK Technical Ceramics)

T

S

,

µµµµ

s

TOM WILLIAMSON: Oscillators for Microcontrollers
APPLICATION NOTE AP-155, June 1983, Intel Corp.

C

X1,2

= 50 pF

C

X1,2

= 150 pF

X2

X2

8

External Memory

External

1 2

4

6

8

10

12 14 16 18 20

10

20

40

60

80

Icc [mA]

Internal

Type of memory:

Frequency [MHz]

22 24 26

28

30

DS87C520,
74AC573,
27C256 (70ns)

DS87C520
(16KB of EPROM)

Internal or External

Program Memor

External

1 2

4

6

8 10 12 14 16 18 20

5

10

20

30

40

Icc [mA]

Internal

Type of memory:

Frequency [MHz]

22 24 26 28 30

DS87C520,
74AC573,
DS2064
(8Kx8 Static RAM)

DS87C520
(1 KB internal MOVX data memory)

50

Internal or External

Data Memory

Zakłócenia elektromagnetyczne

(1/2)

oddziaływanie zewn

ę

trznego pola elektromagnetycznego:

• przepi

ę

cia indukowane w zewn

ę

trznych doprowadzeniach,

ś

cie

ż

kach drukowanych

• przepi

ę

cia indukowane w wewn

ę

trznych doprowadzeniach

(indukcyjno

ś

ci i pojemno

ś

ci poł

ą

cze

ń

struktury wewn

ę

trznej z

wyprowadzeniami)

emisja własnego pola elektromagnetycznego:

• bł

ę

dne wykonanie poł

ą

cze

ń

dla du

ż

ych pr

ą

dów obci

ąż

e

ń

• nadmiarowe, bezzasadne generowanie dodatkowych sygnałów

wyładowania elektrostatyczne

Zakłócenia elektromagnetyczne

(2/2)

wła

ś

ciwa konfiguracja systemu

• eliminacja dodatkowych układów towarzysz

ą

cych, np. 8-bitowy

bufor linii adresowych w C51

• eliminacja wszystkich, zb

ę

dnych zewn

ę

trznych układów, np.

zewn

ę

trznych pami

ę

ci w C51

• test sumy kontrolnej (CRC) całej pami

ę

ci kodu

• stosowanie pami

ę

ci kodu programu programowanej mask

ą

• wył

ą

czenie wszystkich nie u

ż

ywanych sygnałów steruj

ą

cych, np.

ALE, RD# i WR# w C51

wła

ś

ciwy dobór mikrokontrolera, mechanizmów kontroluj

ą

cych działanie

programu:

• programowe

• sprz

ę

towe

szereg tryboelektryczny - zestawienie materiałów pod wzgl

ę

dem biegunowo

ś

ci

i wielko

ś

ci ładunku wytwarzanego podczas zetkni

ę

cia i rozdzielenia dwóch

materiałów:

L. Baranowski: Systemy kontroli ESD.

Elektronik, kwiecie

ń

2003

ludzka r

ę

ka:

+

• azbest
• futro królika
• włókno octanowe
• szkło
• mika
• ludzki włos
• nylon
• wełna
• ołów
• jedwab
• aluminium
• papier

stal
drewno
bursztyn
guma utwardzona
nikiel, mied

ź

srebro, mosi

ą

dz

złoto, platyna
jedwab octanowy
celuloid
poliester
akryl
polietylen
polipropylen
silikon
teflon

—

bawełna

Wyładowania elektrostatyczne

(1/2)

czynno

ś

ci i odpowiadaj

ą

ce im przykładowe ładunki w Voltach dla ró

ż

nych

poziomów wilgotno

ś

ci:

czynno

ś

ci

chodzenie po dywanie
chodzenie po podło

ż

u wykonanym z materiałów

syntetycznych
poruszanie si

ę

w obr

ę

bie stanowiska roboczego

wyci

ą

ganie układu scalonego z szyny z tworzywa

sztucznego
wyci

ą

ganie układu scalonego z podstawki

wyci

ą

ganie układu scalonego ze styropianu

wyci

ą

ganie płytki elektronicznej z opakowania z

tworzywa sztucznego
zapakowanie płytki elektronicznej w wytłoczk

ę

z

tworzywa sztucznego

10%

35.000
12.000

6.000
2.000

11.500
14.500
26.000

21.000

40%

15.000

5.000

800
700

4.000
5.000

20.000

11.000

55%

7.500
3.000

400
400

2.000
3.500
7.000

5.500

wilgotno

ść

wzgl

ę

dna

Wyładowania elektrostatyczne

(2/2)

Safety Device

A

microcontroller

, or any programmed machine,

is not an electronic

brain

, in spite of how it was first introduced. Rather, it is an automaton

that has a precise job to perform, taking into account events and
conditions that are considered when the program is written.

However,

not all events can be taken into account

; some

occurrences are even neglected, since they are supposed to never
happen. Rightly or wrongly, the code is thus made shorter.

If, however, either because the programmer made a mistake or because
a hardware failure produced an unforeseen event, the

program may be

fooled

and the

whole application may fail to work

or even produce

harmful actions.

ST7. 8-BIT MCU FAMILY USER GUIDE.

STMicroelectronics, July 2002

9

Safety Programming

Write better code

. Check what happens if a neglected condition arises.

Lead the execution to a recovery routine in such an event. In short, take
all precautions to prevent the program from crashing in any event. This
is actually a requirement, not a choice. But still, things may happen that
are totally out of the control of the author of the program. For example,
an electromagnetic aggression or a power brownout to the product that
is controlled by the microcontroller. Then, the proper working of the
microcontroller may not be guaranteed and the system fails. This is
when the watchdog can play its part.

Methods of

detecting processor failure

by electronic means are

virtually non-existant. A popular method relies on a timer that acts like
an alarm-clock. The clock is wound up for a certain delay. If it has not
been rewound before the expiration of this delay, the clock perform a
hardware reset to the microcontroller.

WATCHDOG

It is up to the program to

periodically rewind the clock

(the watchdog

timer) to indicate that it is still alive. Actually, it is not a full protection,
since some parts of the program may crash while the part that has been
elected to rewind the timer still functions. It is up to the wise programmer
to find the program segment that is very unlikely to still work while some
other part has crashed. Well implemented, this method gives rather
good results. Of course, resetting the program is not a good way to
recover from a fault, since the crash may have sent commands to the
external world that are themselves faulty. The watchdog timer is actually
a last ditch safety device, somewhat like a lifeboat in a shipwreck.

It has the

ability to induce a full reset of the MCU

if its counter counts

down to zero prior to being reset by the software.

This feature is especially

useful in noisy applications

.

The watchdog timer is a

safety device

rather than a peripheral

Watchdog

w C320/530 Dallas/Maxim (1/3)

główny

generator

/2

17

/2

20

/2

23

/2

26

/2

9

WTRF

kasowanie programowe

ustaw

wewn

ę

trzne

zerowanie

WTRF

kasowanie programowe

ustaw

przerwanie
(adr=63h)

EWT

EA

EWDI

SETB RWT

strat/

/od

ś

wie

ż

anie

Watchdog

WD1,WD0

SMOD1

POR

EPF1

PF1

WDIF

WTRF

EWT

RWT

WDCON (0D8h)

WD1

WD0

T2M

T1M

T0M

MD2

MD1

MD0

CKCON (8Eh)

Timed Access Register: 0AAh, 55h, POR/WDIF/EWT/RWT

TA (0C7h)

Watchdog

w C320/530 Dallas/Maxim (2/3)

Okres wewn

ę

trznych zerowa

ń

przez licznik Watchdoga w

µ

s:

dzielnik

wst

ę

pny

@1,832 MHz

@11,059 MHz

@12 MHz

@33 MHz

2

17

+ 512

71.825

11.898

10.965

3.987

2

20

+ 512

572.646

94.863

87.424

31.791

2

23

+ 512

4.579.214

758.579

699.093

245.216

2

26

+ 512

36.631.755

6.068.304

5.592.448

2.033.617

główny

generator

/2

17

/2

20

/2

23

/2

26

/2

9

WTRF

kasowanie programowe

ustaw

wewn

ę

trzne

zerowanie

WTRF

kasowanie programowe

ustaw

przerwanie
(adr=63h)

EWT

EA

EWDI

SETB RWT

strat/

/od

ś

wie

ż

anie

Watchdog

WD1,WD0

Watchdog

w C320/530 Dallas/Maxim (3/3)

Uruchomienie Watchdoga:

CK_CON EQU

1000 0000b ; 2

23

stopie

ń

podziału dzielnika wst

ę

pnego

TA_AA

EQU

0AAh

; dost

ę

p do bitów w rejestrze WDCON

TA_55

EQU

55h

; chronionych zapisem czasowym

Reset_WD:

ORL

CKCON, #CK_CON

; programowanie stopnia
; podziału dzielnika

MOV

TA, #TA_AA

; start Watchdoga

MOV

TA, #TA_55

SETB RWT

MOV

TA, #TA_AA

; odblokowanie wewn

ę

trznego zerowania

MOV

TA, #TA_55

; przez Watchdog

SETB EWT

o

k

n

a

c

z

a

s

o

w

e

Watchdog - MSP430

Write to WDTCTL

< > 5Ah

= 5Ah

CNTCL

Restart Watchdog at 0000

ACLK

(32768 Hz)

MCLK

SSEL

0

1

EN

Clear

CLK

2

6

2

9

2

13

2

15

16-Bit Counter

HOLD

11 10

01 00

IS1,IS0

Set

WDTIFG

POR

IRQA

Timer Mode

Reset

0

1

GIE

General Interrupt
Flag

Interrupt

Timer Mode
(0FFF4h)
priority 10

W

a

tc

h

d

o

g

M

o

d

e

Password

Watchdog Interrupt Enable Flag

WDTIE

T

M

SEL

PUC

(Watchdog
Mode
(0FFFEh)
priority 15
(highest)

HOLD

NMIES

NMI

TMSEL CNTCL

SSEL

IS1

IS0

WDTCTL

(120h)

read access = 69h

write access = 5Ah