Siemens SIMATIC S7-300 Manual page 242

Description of Functions
Monitoring/error If MD20 = 0 is input, all monitoring functions are active.
diagnostics
Individual monitoring functions can be inactivated by entering 0 in the desig-
nated bit of MD20.
You can deactivate the error messages using the single function "parking
axis" (see Section 9.3.2).
Table 9-12 Error diagnostics – Absolute encoder
Diagnosis
Voltage monitoring Encoder power failure
Error in absolute encoder Error in protocol for data transfer between
absolute encoder and FM 354
Warning
!
Hardware monitoring functions should be skipped only for test purposes,
since positioning errors may destroy the machine.
When voltage monitoring is deactivated and the power supply to the encod-
ers or the FM is switched off, an immediate failure in absolute value signal-
ing can cause drive movements if:
Encoder
See Section 4.5.
connection
9-66
Cause
an operating mode other than open–loop control is active
and follow–up mode is deactivated
and the servo enable is activated or not parameterized.
Error message
Diagnostic interrupt, external channel error
(see Troubleshooting, 11-4)
Diagnostic interrupt, external channel error
(see Troubleshooting, 11-4)
FM 354 Servo Drive Positioning Module