libmodbus/doc/modbus_write_and_read_registers.txt

modbus_write_and_read_registers(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
--------
linkmb:modbus_read_registers[3]
linkmb:modbus_write_register[3]
linkmb:modbus_write_registers[3]


AUTHORS
-------
The libmodbus documentation was written by Stéphane Raimbault
<stephane.raimbault@gmail.com>