F_IOPortWrite

The function F_IOPortWrite can be used to write to an I/O position with a width of eSize. See also description of the F_IOPortRead function.

Notice

Hardware damage

A direct hardware access is not a problem, as long as data is only read. Write access can result in crashes and/or destroy the hardware or the data on the storage media. This function can damage the hardware to such an extent that it is no longer bootable.

FUNCTION F_IOPortWrite : BOOL

Inputs

VAR_INPUT
    nAddr  : UDINT;
    eSize  : E_IOAccessSize;
    nValue : DWORD;
END_VAR

Name	Type	Description
nAddr	UDINT	I/O port address
eSize	E_IOAccessSize	Number of data bytes to be written (type: E_IOAccessSize).
nValue	DWORD	Value to be written.

Return parameter	Description
TRUE	No error
FALSE	Error

Sample code in ST:

In the following example a PLC Function block for direct control of a PC speaker is implemented with the aid of the I/O -Port functions.

Interface:

FUNCTION_BLOCK FB_Speaker
(* Sample code from: "PC INTERN 2.0", ISBN 3-89011-331-1, Data Becker *)
VAR_INPUT
    freq     : DWORD := 10000; (* Frequency [Hz] *)
 tDuration   : TIME := T#1s; (* Tone duration *)
    bExecute : BOOL; (* Rising edge starts function block execution *)
END_VAR
VAR_OUTPUT
    bBusy  : BOOL;
    bError : BOOL;
    nErrID : UDINT;
END_VAR
VAR
    fbTrig : R_TRIG;
    nState : BYTE;
    sts61H : DWORD;
    cnt42H : DWORD;
    cntLo  : DWORD;
    cntHi  : DWORD;
    timer  : TON;
END_VAR

Implementation:

fbTrig( CLK := bExecute );
CASE nState OF
0:
IF fbTrig.Q THEN
    bBusy := TRUE;
    bError := FALSE;
    nErrID := 0;
    timer( IN := FALSE );

    IF F_IOPortWrite( 16#43, NoOfByte_Byte, 182 ) THEN

        cnt42H := 1193180 / freq;
        cntLo := cnt42H AND 16#FF;
        cntHi := SHR( cnt42H, 8 ) AND 16#FF;

        F_IOPortWrite( 16#42, NoOfByte_Byte, cntLo ); (* LoByte *)
        F_IOPortWrite( 16#42, NoOfByte_Byte, cntHi ); (* HiByte *)

        timer( IN := TRUE, PT := tDuration );

        sts61H := F_IOPortRead( 16#61, NoOfByte_Byte );
        sts61H := sts61H OR 2#11;
        F_IOPortWrite( 16#61, NoOfByte_Byte, sts61H ); (* speaker ON *)

        nState := 1;
    ELSE
        nState := 100;
    END_IF
END_IF

1:
timer( );
IF timer.Q THEN

    sts61H := F_IOPortRead( 16#61, NoOfByte_Byte );
    sts61H := sts61H AND 2#11111100;
    F_IOPortWrite( 16#61, NoOfByte_Byte, sts61H ); (* speaker off *)
    bBusy := FALSE;
    nState := 0;
END_IF

100:
bBusy := FALSE;
bError := TRUE;
nErrID := 16#8000;
nState := 0;

END_CASE
 
Test application:

PROGRAM MAIN
VAR
    fbSpeaker : FB_Speaker;
    bStart : BOOL;
END_VAR
 

fbSpeaker( freq:= 5000,
tDuration:= t#1s,
bExecute:= bStart );

Requirements

Development environment	Target system type	PLC libraries to include (Category group)
TwinCAT v3.1.0	PC or CX (x86, x64, ARM)	Tc2_System (System)