omron PLC C200HX hang!!!!!

My plc C200HX is link to a humidity sensor though RS232 by periperal port. All the moment the reading by the no protocol method is no problem. But, it will be a sudden happen frame and parity error. Then, it will cause my periperal port error. Then, i need to restart the peripheral port by the internal flag. But, sometimes the plc will detect long cycle when restarting the peripheral port and it will cause my whole PLC error and the only way to reset it is to turn off and on the power supply plc again. My question is why detect long cyle, the whole plc will become hang???? any suggestion to overcome this problem.?????

Check the manual. You can go into the setup area and increase the scan time to suit you application. It is probably set at fixed value of 120ms.
beerchug