Файл: Basic for PIC Microcontrollers (M. Nebojsa, 2001).pdf

Basic for PIC Microcontrollers

69

Syntax:

RANDOM Variable

Description:

Instruction RANDOM stores pseudo-random number to variable. Variable should be 16-

bit.

Example:

W0 var word

Main :

random W0

‘

Put random number to variable W0

lcdoout #W0

‘

Display random number on LCD

goto Main

End

Syntax:

RCTIME Pin, State, Variable

Description:

RCTIME measures time period during which "pin" remains in a certain state. If ihe state

remains unchanged variable is set to zero. RCTIME can be used for reading potentiometer

or some other resistive element based on the time necessary for filling RC constant.

Typical resistance measured is within 5K~50K range.

Resolution depends n oscillator frequency. 4MHz oscillator has 10us resolution, while

20MHz oscillator has 2us resolution.

Example:

W0 var word

Main :

low PORTA.0

‘ Discharge the condenser

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pause 10

‘

Discharging lasts for 10ms

rctime PORTA.0, 0, W0

‘ Measure duration of charging

lcdout #W0

‘

Display value of W0 on LCD

goto Main

End

Syntax:

READ Address, Variable

Description:

Instruction READ reads data from internal EEPROM memory from the specified address

and stores the result to "Variable". This instruction can only be used with PIC

microcontrollers which have EEPRO M built in the chip. If microcontroller is supplied with

external EEPROM, instruction I2CREAD should be used instead.

Example:

B0 var byte

W var word

Main :

READ 5, B0

‘

read data from EEPROM, address 5 and put it to variable B0

READ 6, W.BYTE0

‘

load 16-bit data

READ 7, W.BYTE1

‘

from addresses 6 and 7 to variable W

Loop: goto Loop

End

Syntax:

READCODE Address, Variable

Example:

Wo var word

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Introduction

4.1 @

4.17 GOSUB

4.33 LOOKUP2

4.49 RETURN

4.2 ASM..ENDASM

4.18 GOTO

4.34 LOW

4.50 REVERSE

4.3 ADCIN

4.19 HIGH

4.35 NAP

4.51 SELECT-CASE

4.4 BRANCH

4.20 HSERIN

4.36 OUTPUT

4.52 SERIN

4.5 BRANCHL

4.21 HPWM

4.37 OWIN

4.53 SERIN2

4.6 BUTTON

4.22 HSEROUT

4.38 OWOUT

4.54 SEROUT

4.7 CALL

4.23 I2CREAD

4.39 PAUSE

4.55 SEROUT2

4.8 CLEAR

4.24 I2CWRITE

4.40 PAUSEUS

4.56 SHIFTIN

4.9 CLEARWDT

4.25 INPUT

4.41 POT

4.57 SHIFTOUT

4.10 COUNT

4.26 IF-THEN-ELSE

4.42 PULSIN

4.58 SLEEP

4.11 DATA

4.27 LCDOUT

4.43 PULSOUT

4.59 SOUND

4.12 DTMFOUT

4.28 LCDIN

4.44 PWM

4.60 STOP

4.13 EEPROM

4.29 {LET}

4.45 RANDOM

4.61 SWAP

4.14 END

4.30 LOOKDOWN

4.46 RCTIME

4.62 TOGGLE

4.15 FREQOUT

4.31 LOOKDOWN2

4.47 READ

4.63 WRITE

4.16 FOR-NEXT

4.32 LOOKUP

4.48 READCODE

4.64 WRITECODE

4.65 WHILE-WEND

4.49 RETURN

Return from the subroutine

Syntax:

RETURN

Description:

Instruction RETURN executes return from the program routine which program jumped

onto via GOSUB instruction.

Example:

Main :

gosub portb_on

‘

call a subroutine init_ram

Loop : goto Loop

portb_on:

PORTB=$FF

‘

Light all port B diodes

return

‘

return from subroutine

End

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Syntax:

REVERSE Pin

Description:

Instruction REVERSE inverts orientation of a specified pin. If pin is input, REVERSE

changes it to output and vice versa.

Example:

Main :

reverse PORTA.0

‘ Change orientation of RA0 pin

Loop : goto Loop

End

Syntax:

SELECT CASE Var

CASE Expression1 {, Expression}

Instructions...

CASE Expression2 {, Expression}

Instructions...

CASE Expression3 {, Expression}

Instructions...

CASE ELSE

Instructions...

END SELECT

Description:

Although conditional SELECT -CASE branching can be made with multiple IF -THEN

instructions, it is easier and more sensible to use this instruction in certain

situations. Instruction allows "Expression" to be a constant, one of the constants or a

comparison to a certain constant.

Example:

W var byte