modbus_write_and_read_registers(3) [debian man page]

MODBUS_WRITE_AND_REA(3) 					 Libmodbus Manual					   MODBUS_WRITE_AND_REA(3)

NAME

       modbus_write_and_read_registers - write and read many registers in a single transaction

SYNOPSIS

       int modbus_write_and_read_registers(modbus_t *ctx, int write_addr, int write_nb, const uint16_t *src, int read_addr, int read_nb, const
       uint16_t *dest);

DESCRIPTION

       The modbus_write_and_read_registers() function shall write the content of the write_nb holding registers from the array src to the address
       write_addr of the remote device then shall read the content of the read_nb holding registers to the address read_addr of the remote device.
       The result of reading is stored in dest array as word values (16 bits).

       You must take care to allocate enough memory to store the results in dest (at least nb * sizeof(uint16_t)).

       The function uses the Modbus function code 0x17 (write/read registers).

RETURN VALUE

       The modbus_write_and_read_registers() function shall return the number of read registers if successful. Otherwise it shall return -1 and
       set errno.

ERRORS

       EMBMDATA
	   Too many registers requested, Too many registers to write

SEE ALSO

       modbus_read_registers(3) modbus_write_register(3) modbus_write_registers(3)

AUTHORS

       The libmodbus documentation was written by Stephane Raimbault <stephane.raimbault@gmail.com[1]>

NOTES

	1. stephane.raimbault@gmail.com
	   mailto:stephane.raimbault@gmail.com

libmodbus 3.0.3 						    05/26/2012						   MODBUS_WRITE_AND_REA(3)

MODBUS_MAPPING_NEW(3)						 Libmodbus Manual					     MODBUS_MAPPING_NEW(3)

NAME

       modbus_mapping_new - allocate four arrays of bits and registers

SYNOPSIS

       modbus_mapping_t modbus_mapping_new(int nb_bits, int nb_input_bits, int nb_registers, int nb_input_registers);*

DESCRIPTION

       The modbus_mapping_new() function shall allocate four arrays to store bits, input bits, registers and inputs registers. The pointers are
       stored in modbus_mapping_t structure. All values of the arrays are initialized to zero.

       If it isn't necessary to allocate an array for a specific type of data, you can pass the zero value in argument, the associated pointer
       will be NULL.

       This function is convenient to handle requests in a Modbus server/slave.

RETURN VALUE

       The modbus_mapping_new() function shall return the new allocated structure if successful. Otherwise it shall return NULL and set errno.

ERRORS

       ENOMEM
	   Not enough memory

EXAMPLE

	   /* The fist value of each array is accessible from the 0 address. */
	   mb_mapping = modbus_mapping_new(BITS_ADDRESS + BITS_NB,
					   INPUT_BITS_ADDRESS + INPUT_BITS_NB,
					   REGISTERS_ADDRESS + REGISTERS_NB,
					   INPUT_REGISTERS_ADDRESS + INPUT_REGISTERS_NB);
	   if (mb_mapping == NULL) {
	       fprintf(stderr, "Failed to allocate the mapping: %s
",
		       modbus_strerror(errno));
	       modbus_free(ctx);
	       return -1;
	   }

SEE ALSO

       modbus_mapping_free(3)

AUTHORS

       The libmodbus documentation was written by Stephane Raimbault <stephane.raimbault@gmail.com[1]>

NOTES

	1. stephane.raimbault@gmail.com
	   mailto:stephane.raimbault@gmail.com

libmodbus 3.0.3 						    05/26/2012						     MODBUS_MAPPING_NEW(3)