Mitsubishi Electric FR-E700EX Instruction Manual page 208

Communication operation and setting
REMARKS
 Pr.121 is valid only when Mitsubishi inverter (computer link operation) protocol is selected. Pr.121 is not valid when Modbus-
RTU communication protocol is selected.
 How the drive unit operates at a communication error differs according to the Pr. 502 Stop mode selection at communication error
setting.
(2) Signal loss detection (Pr.122)
 If a signal loss (communication stop) is detected between the drive unit and master as a result of a signal loss detection,
a communication fault (E.PUE) occurs and the drive unit trips. (as set in Pr.502).
 When the setting is "9999", communication check (signal loss detection) is not made.
 When the setting value is "0" (initial value), RS-485 communication can be made. However, a communication fault
(E.PUE) occurs as soon as the drive unit is switched to the operation mode (Network operation mode in the initial setting)
with the command source.
 A signal loss detection is made when the setting is any of "0.1s to 999.8s". To make a signal loss detection, it is
necessary to send data (refer to Mitsubishi inverter protocol control code (Refer to page 212), Modbus-RTU
communication protocol (Refer to page 223)) from the computer within the communication check time interval. (The drive
unit makes communication check (clearing of communication check counter) regardless of the station number setting of
the data sent from the master).
 Communication check is made from the first communication in the operation mode with command source valid (Network
operation mode in the initial setting).
Example: PU connector communication, Pr.122 = "0.1 to 999.8s"
Operation mode
Computer
Drive unit
Drive unit
Computer
Communication
check counter
Always set the communication check time interval before starting operation to prevent hazardous conditions.
Data communication is not started automatically but is made only once when the computer provides a
communication request. If communication is disabled during operation due to signal cable breakage etc., the
drive unit cannot be stopped. When the communication check time interval has elapsed, the drive unit trips
(E.PUE).
The motor can be coasted to a stop by turning ON its RES signal or by switching power OFF.
If communication is broken due to signal cable breakage, computer fault, etc. the drive unit does not detect
such a fault. This should be fully noted.
206
External NET
Pr.122
ALM OFF
Check start
CAUTION
Fault (E.PUE)
Time
ON