Siemens 505-2571

Troubleshooting 4-3SIMATIC 505-2571 Program Port Expander Manual

the XMT indicator does not flash within 2 seconds of receiving a signal

(RCV indicator flashes), it indicates that the PPX:505-2571 is not

responding to the signal. Refer to the information below for possible causes.

First, check to ensure that the baud rate settings on both the PPX:505-2571

and the operator interface are set to the same data rate. If you note a

problem, set both to the same baud rates and retry

NOTE:

ou must remove power from the PPX:505-2571 module, change the

DIP switch settings, and repower the module before the new baud rate

selection will become effective.

If you are using a RS–232 port and your device is NOT configured for

hardware handshaking, ensure that hardware handshaking is DISABLED

(DIP switch position 3 for the port in the OFF position). See T

able 2-1 and

Figure 2-1.

If you are using a RS–232 port and your device is configured for hardware

handshaking, ensure that the handshaking wires are properly connected

(see the documentation for the connected device). In some cases you can

check out a handshake wiring problem by temporarily setting hardware

handshaking to DISABLED (port DIP switch position 3 set to the OFF

position). If the PPX:505-2571 responds to the attached device (XMT LED

flashes), then you probably have a wiring problem.

The attached device must issue and respond to task code packets as defined

in the Non–Intelligent T

erminal Protocol (NITP). If you are unsure of this

fact, you can attach the device directly to the programming port to

determine if it works properly

. If it does not work and cabling/configuration

items discussed in other sections above have been checked, then you

probably have a protocol problem. If it does work, there is still a chance that

the device is using T

ransparent Byte Protocol (TBP), which is not supported

in this version of the PPX:505-2571. Most application programs and

operator interface devices that can use TBP allow you to force the use of

Non–Intelligent Protocol (NITP), which is supported.

If you experience intermittent communications failures, you may be

experiencing noise on the communications cable which interferes with data

transmission. If you are communicating at rates higher than 1200 baud, you

can reduce the baud rate to check for improvement. If reducing the baud

rate does correct the proble, you most likely have a noise problem. Y

should first ensure that you have not exceeded the maximum distances for

cabling lengths (50 feet for RS–232 and 4000 feet for RS–422). Also check

for proper grounding of the cable shields; we recommend connecting the

shield at one end only. Longer cable runs may be subject to ground loops;

you may require the addition of an electrical isolation device.

Module Response

Problems

Baud Rate

Mismatch

Hardware

Handshaking Err

otocol Pr

oblems