Sistemi Elettronici Programmabili 13-1

MULTI OSC+

CLOCK FILTER

LVD

POWERSUPPLY

CONTROL

8 BIT COREALU

PROGRAM MEMORY

RAM

I2C

PORT A

SPI

PORT B

16-BIT TIMER A

PORT C

8-BIT ADC

16-BIT TIMER B

WATCHDOG

INTERNALCLOCK

AD

DR

ES

S A

ND

DA

TA

BU

S

OSC1

OSC2

VDD

VSS

nRESET

PA7..0(8 bits)

PB7..0(8 bits)

PC5..0(6 bits)

ST7: Block Diagram

Sistemi Elettronici Programmabili 13-2

ST72254 - Package

Sistemi Elettronici Programmabili 13-3

ST72254 Memory Map

Sistemi Elettronici Programmabili 13-4

ST72254 – Interrupt Vector

Sistemi Elettronici Programmabili 13-5

ST

7225

4 R

egis

ters

(1)

Sistemi Elettronici Programmabili 13-6

ST

7225

4 R

egis

ters

(2)

Sistemi Elettronici Programmabili 13-7

ST72254 Registers (IO)

Sistemi Elettronici Programmabili 13-8

ST72254 Registers (Timer)

Sistemi Elettronici Programmabili 13-9

ST72254 Registers (ADC)

Sistemi Elettronici Programmabili 13-10

IO P

ort

: B

lock

Dia

gra

m

Sistemi Elettronici Programmabili 13-11

IO Port Configurations - Input

Sistemi Elettronici Programmabili 13-12

IO Port Configurations – Output Opendrain

Sistemi Elettronici Programmabili 13-13

IO Port Configurations – Output Push Pull

Sistemi Elettronici Programmabili 13-14

IO Port: Registers

Sistemi Elettronici Programmabili 13-15

ADC: Overview (1)

• 8-BIT SUCCESSIVE APPROXIMATIONS CONVERTER WITH UP TO 8

ANALOG CHANNELS

• FEATURE :

– Accuracy : 1 LSB

– Total Unajusted Error MAX : 1 LSB

– Conversion time : 24 CPU cycle ie 3µs at full speed (8MHz)

• FLAGS

– COCO : end of conversion (Status flag)

– ADON : ADC on/off bit (to reduce power consumption)

Sistemi Elettronici Programmabili 13-16

ADC: Overview (2)

• LOW CONSUMPTION MODES– Wait mode doesn't affect the ADC– Halt mode stops the ADC.

• HARDWARE– ST72334 and ST725xx : Vdda and Vssa must be connected

externally respectivelly to Vdd and Vss through decoupling capacitors.

– ST72254 : connection done internally

• RATIOMETRIC In the Functionnal Range– If analog voltage input > Vdd :

converted result = FFh (no overflow indication)– If analog voltage input < Vss :

converted result = 00h (no underflow indication)

Sistemi Elettronici Programmabili 13-17

ADC: Block Diagram

Sistemi Elettronici Programmabili 13-18

ADC: Registers

Sistemi Elettronici Programmabili 13-19

Tim

er:

Blo

ck D

iag

ram

Sistemi Elettronici Programmabili 13-20

Tim

er:

Blo

ck D

iag

ram

(H

)

Sistemi Elettronici Programmabili 13-21

Tim

er:

Blo

ck D

iag

ram

(L

)

Sistemi Elettronici Programmabili 13-22

Tim

er:

Rea

d S

equ

ence

Sistemi Elettronici Programmabili 13-23

Tim

er:

Inp

ut

Cap

ture

Sistemi Elettronici Programmabili 13-24

Tim

er:

Ou

tpu

t C

om

par

e

Sistemi Elettronici Programmabili 13-25

TIMER: PWM Mode

• Automatic generation of a Pulse Width Modulated signal

• Period &pulse lenght set by software: – The first Output Compare Register OC1R contains the length of

the pulse– The second Output Compare Register OCR2 contains the period

of the pulse

• Resolution up to 100 steps at 20 KHz (fCPU =4 MHz): 1% of accuracy on the duty cycle

t

T

Sistemi Elettronici Programmabili 13-26

Timer: PWM Flow

When the free running counter reaches

OC2R register value

When the free running counter reaches

OC1R register value

Free running counter is initialized to FFFCh

OLVL2 bit level is applied on the OCMP1 pin

ICF1 bit is set

OLVL1 bit level is applied on the OCMP1 pin

Sistemi Elettronici Programmabili 13-27

Timer: PWM Counter

OCMP1 Ouput Compare pinTimer output

FFFFh

Compare 1

0000h

Compare 2

FFFCh

Ttimer × 65535Tmax =

OLVL1=0

OLVL2= 1

FREE RUNNING COUNTER VALUE

time

time

Sistemi Elettronici Programmabili 13-28

Tim

er:

CR

1

Sistemi Elettronici Programmabili 13-29

Tim

er:

CR

2

Sistemi Elettronici Programmabili 13-30

Tim

er:

SR

Sistemi Elettronici Programmabili 13-31

Schmitt Trigger: Caratteristica Inverter

Sistemi Elettronici Programmabili 13-31t

t

Vin

Vout

Sistemi Elettronici Programmabili 13-32

Schmitt Trigger: Caratteristica

Vin

Vout

Sistemi Elettronici Programmabili 13-33

Schmitt Trigger: Inverter - Commutazioni Spurie

t

t

Vin

Vout

Sistemi Elettronici Programmabili 13-34

Schmitt Trigger: Commutazione

t

t

Vin

Vout