各位坛友好，我公司的老设备最近发生故障，PLC SIEMENS SIMATIC 6ES5524-3UA13模块上有一个红色指示灯常亮(见图)，请教是什么故障表示？还有电脑上显示的故障是：
unrecoverable error on the serial communication line.
switch off then switch on the warper by turning the main switch.
in case the error persists,a tech-nical assistance is required.
automatic functioning is not avail-able.
if a warping process has to be carried out,rotate the key-selector towards "emergency" then keep the "broken
end" push-button pressed for about 5 seconds.
盼各位朋友帮我看看，谢谢大家了！

从字面讲还是挺清楚的，最后一句是讲如何操作的。