FB_NovRamReadWriteEx

FB_NovRamReadWriteEx 1:

The FB_NovRamReadWriteEx function block accesses the NOV-RAM (e.g. of the FCxxxx-0002 fieldbus cards, CX9000 NOVRAM, etc.) from a PLC program. A rising edge at the bRead or bWrite input activates the function block and a corresponding number of data bytes are read from the NOV-RAM or written to the NOVRAM. If both inputs: bRead and bWrite are set at the same time, the data is first written to the NOVRAM and then read back. The difference to the FB_NovRamReadWrite function block is that the address offset can be specified in the NOVRAM for write and read accesses. The function block also checks the permitted type of access to the NOVRAM memory and, if necessary, copies the data byte by byte into the NOVRAM memory instead of using a MEMCPY. The NOVRAM of the CX9000 only allows byte accesses, for example, and the FB_NovRamReadWrite function block would return an error in this case.

Comments:

To determine the address pointer to the NOVRAM, an instance of the ADSREAD function block is used internally by the FB_NovRamReadWriteEx function block. However, this address pointer is only redetermined the first time the FB_NovRamReadWriteEx function block is called and when nDevId is changed. Several PLC cycles are required for this. The NOVRAM memory is accessed directly for writing data to or reading data from the NOVRAM. This enables data to be written or read in the same PLC cycle. The maximum byte length of the NOVRAM is also determined internally and the maximum length of the data that can be read or written is limited to this length.

Inputs

VAR_INPUT
    nDevId     : UDINT;
    bRead      : BOOL;
    bWrite     : BOOL;
    cbSrcLen   : UDINT;
    cbDestLen  : UDINT;
    pSrcAddr   : PVOID;
    pDestAddr  : PVOID;
    nReadOffs  : UDINT;
    nWriteOffs : UDINT;
    tTimeOut   : TIME := DEFAULT_ADS_TIMEOUT;
END_VAR

Name	Type	Description
nDevId	UDINT	The device ID of a NOVRAM card. The ID is used to specify the NOVRAM of an FCxxxx-0002 card that is to be accessed for writing or reading with the function block. The device IDs are specified by the TwinCAT system during the hardware configuration.
bRead	BOOL	A positive edge at this input activates the function block and cbDestLen data is copied from the NOVRAM (from address offset NULL) into the buffer with the address pDestAddr.
bWrite	BOOL	A positive edge at this input activates the function block and copies cbSrcLen data from the buffer with the address pSrcAddr into the NOVRAM (from address offset NULL).
cbSrcLen	UDINT	The byte length of the data to be written to the NOVRAM.
cbDestLen	UDINT	The byte length of the data to be read from the NOVRAM.
pSrcAddr	PVOID	The address pointer to a data buffer containing the data to be written into the NOV-RAM. The address pointer can be determined via the ADR operator.
pDestAddr	PVOID	The address pointer to a data buffer into which the read NOV-RAM data is to be copied.
nReadOffs	UDINT	The address offset in the NOVRAM from which data are to be read.
nWriteOffs	UDINT	The address offset in the NOVRAM from which data are to be written.
tTimeOut	TIME	Specifies the time-out period that must not be exceeded when executing the command/function.

Outputs

VAR_OUTPUT
    bBusy     : BOOL;
    bError    : BOOL;
    nErrId    : UDINT;
    cbRead    : UDINT;
    cbWrite   : UDINT;
END_VAR

Name	Type	Description
bBusy	BOOL	This output is set when the function block is activated, and remains set until execution has been completed.
bError	BOOL	This output is set if an error occurs during execution.
nErrId	UDINT	Returns the ADS error number when the bError output is set.
cbRead	UDINT	Number of successfully read data bytes.
cbWrite	UDINT	Number of successfully written data bytes.

Sample:

PROGRAM MAIN
VAR
    fbNovRamReadWrite : FB_NovRamReadWriteEx;
    bRead             : BOOL;
    bWrite            : BOOL;
    fromNovRam        : ARRAY[1..100] OF BYTE;
    toNovRam          : ARRAY[1..100] OF BYTE;
    bBusy             : BOOL;
    bError            : BOOL;
    nErrID            : UDINT;
    cbRead            : UDINT;
    cbWrite           : UDINT;
    readOffs          : UDINT :=0;
    writeOffs         : UDINT:=0;
    cbToWrite         : UDINT := 100;
    cbToRead          : UDINT := 100;
END_VAR

In the sample, a rising edge at the bRead input reads 100 bytes of data from the NOV-RAM and copies them into the fromNovRam array.

Requirements

Development environment	Target platform	IO Hardware	PLC libraries to be integrated (category group)
TwinCAT v3.1.0	PC or CX (x86)	FCxxxx cards with NOVRAM (FCxxxx-0002)	Tc2_IoFunctions (IO)