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IA3341 Linux User’s Manual Programmer’s Guide

6-17

Write register values via function code 6 or 16

int

mbtcp_write_regs(

void *hndl,

unsigned int tmout,

unsigned short start_addr,

unsigned short count,

unsigned short reg_val[]

);

Input:

<hndl> MODBUS TCP connection handler

<tmout> communication timeout in second

<start_addr> starting address

<count> quantity of registers

<reg_val> an array to hold register values

Output: none

Return:

0 for success, negative value for failure from API, and positive value for failure

from MODBUS TCP server

-1 argument error

-2 failed to send MODBUS TCP request to MODBUS TCP server

-3 failed to receive MODBUS TCP response from MODBUS TCP server

-4 disconnection with MODBUS TCP server

-5 illegal MODBUS TCP response message received

-6 unexpected MODBUS TCP response message received

1 bad function code

2 address out of range

3 bad write count or bad write value

4 internal gateway failure

6 unable to accept the MODBUS request

Programs that use the API functions must follow the proper usage. To begin with, call mbtcp_init()

once to initialize the MODBUS TCP connection environment. Next, call mbtcp_connect() to

create a MODBUS TCP connection handler and connect to the MODBUS TCP server. Then, call

mbtcp_read_regs() and mbtcp_write_regs() to read register values and write register values,

respectively. Before the program exits, call mbtcp_disconnect() to close its MODBUS TCP

connection and destroy the specified connection handler, and then call mbtcp_release() to release

the MODBUS TCP connection environment. The API functions cannot be used by multiple

threads at the same time.