int ModbusServer::configureHoldingRegisters(int startAddress, int nb)
{
  if (startAddress < 0 || nb < 1) {
    errno = EINVAL;

    return -1;
  }

  size_t s = sizeof(_mbMapping.tab_registers[0]) * nb;

  _mbMapping.tab_registers = (uint16_t*)realloc(_mbMapping.tab_registers, s);

  if (_mbMapping.tab_registers == NULL) {
    _mbMapping.start_registers = 0;
    _mbMapping.nb_registers = 0;

    return 0;
  }

  memset(_mbMapping.tab_registers, 0x00, s);
  _mbMapping.start_registers = startAddress;
  _mbMapping.nb_registers = nb;

  return 1;
}