finslib_memory_area_read_word( sys, start, data, num_word );
Parameters
| Parameter | Type | Description |
|---|---|---|
sys |
struct fins_sys_tp * |
A pointer to a structure with the FINS context |
start |
const char * |
An ASCII string describing the first memory element to retrieve |
data |
unsigned char * |
Pointer to the buffer where the result must be stored |
num_word |
size_t |
The number of words to return |
Return Value
| Type | Description |
|---|---|
int |
A return value from the list FINS_RETVAL_... indicating the result of the query |
Description
The function finslib_memory_area_read_word() can be used to retrieve a block of 16 bit words from a memory area in a remote PLC. The connection with the PLC should already be present before this function is called.
Data is transferred unmodified from the FINS data stream to the caller supplied buffer. As this function returns a number of words, the size of the data buffer in bytes should be at least twice the number of words requested. Enough dataspace is the responsibility of the calling function, but finslib_memory_area_read_word() will return an error if a NULL pointer is provided for data storage.
The start of the memory area is provided as an ASCII string which represents the starting address in human readable format. Example formats are CIO20 and W100.
The requested number of words is not limited by the amount of data a PLC can send in one FINS packet because finslib_memory_area_read_word() will automatically use multiple request at the FINS layer if the dataset will be too large.
The return value is either FINS_RETVAL_SUCCESS when the function succeeded, or one of the other FINS_RETVAL_ values if an eror occurs. In the latter case the data in the return buffer is unreliable and should not be used.
See Also
-
FINS_RETVAL...– Libfins function return code list -
FINS_DATA_TYPE...– Libfins data types finslib_memory_area_read_bit();finslib_memory_area_write_bit();finslib_memory_area_write_word();finslib_multiple_memory_area_read();