MB_FileWr()

MB_FileWr() is called when a Modbus master sends a Function Code 21 command. MB_FileWr() writes a single integer value to a file. As mentionned in the Modbus specifications, a file is an organization of records. Each file can contain up to 10,000 records (addressed from 0 to 9999). You must 'map' the File/Record/Ix to the actual application's corresponding data. MB_FileWr() should only be called by µC/Modbus.

Prototype

void MB_FileWr (CPU_INT16U file_nbr,
CPU_INT16U record_nbr,
CPU_INT16U ix,
CPU_INT08U record_len,
CPU_INT16U val,
CPU_INT16U * perr)

Arguments

file_nbr

Is the number of the desired file.

record_nbr

Is the desired record within the file, a number between 0 and 9999.

ix

Is the desired entry in the specified record.

record_len

Is the total length of the record.

val

Is the value to write to the file/record.

perr

Is a pointer to a variable that will contain an error code based on the outcome of the call. Your code thus needs to return one of the following error codes:

MODBUS_ERR_NONE

the specified file/record/entry is valid and your code is returning its current value.

MODBUS_ERR_FILE

if the specified file_nbr is not a valid file number in your product.

MODBUS_ERR_RECORD

if the specified record_nbr is not a valid record number in the specified file.

MODBUS_ERR_IX

if the specified ix is not a valid index into the specified record.

Returned Value

None.

Notes / Warnings

Code is enabled when MODBUS_FC21_EN is set to DEF_ENABLED in your product’s mb_cfg.h file.

Called By:

MBS_FC21_FileWr() in mbs_core.c

Example

In this example, we have two ‘files’ that we implemented as an array of 16-bit integers.

#define     APP_MAX_FILES 2
#define     APP_FILE_MAX_RECORDS   10
#define     APP_FILE_MAX_VALUES   100


CPU_INT16U  AppFile[APP_MAX_FILES][APP_FILE_MAX_RECORDS][APP_FILE_MAX_VALUES];



CPU_INT16U  MB_FileWr (CPU_INT16U   file_nbr, 
                       CPU_INT16U   record_nbr, 
                       CPU_INT16U   ix, 
                       CPU_INT08U   record_len, 
                       CPU_INT16U   val, 
                       CPU_INT16U  *perr)
{
    *perr = MODBUS_ERR_NONE;
    if (file_nbr >= APP_MAX_FILES) {
        *perr = MODBUS_ERR_FILE;
        return;
    }
    if (record_nbr >= APP_FILE_MAX_RECORDS) {
        *perr = MODBUS_ERR_RECORD;
        return;
    }
    if (ix >= APP_FILE_MAX_VALUES) {
        *perr = MODBUS_ERR_IX;
        return;
    }
    CPU_CRITICAL_ENTER();
    AppFile[file_nbr][record_nbr][ix] = val;
    CPU_CRITICAL_EXIT();
}