Hitachi CONVENTION 14 Instruction Manual page 199

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Network Detection Signal (Integrated ModBus)
The Network Detection Signal output indicates the general status of network
communications (integrated ModBus communication). The inverter has a
programmable watchdog timer to monitor network activity. Parameter C077 sets the
time-out period. If communications stop or pause longer than the specified time-out
period, the NDc output turns ON.
Option Terminal
Code Symbol
08 NDc
Valid for inputs:
Required settings
Notes:
To disable the communications watchdog timer,
set C077=00.00 sec.
If you set Communications Error Select to
"Disable" (C076=02), you still have the option of
using the Network Detection Signal and setting
the watchdog time-out period with C077.
Additionally, the inverter can respond to a communications time-out in various ways.
Refer to the following diagram (top of next page). You configure the desired response via
function C076, Communications Error Select. This selects whether or not you want the
inverter to trip (alarm with error code E60) and whether to stop the motor or just let it
coast. Together, parameters C076 and C077 set the network detection watchdog time-
out and the inverter's response.
Function Name State
Network
Disconnection
Signal (ModBus)
OFF
11, AL0 – AL2
C076, C077
ON when the communication watchdog timer (period
specified by C077) has timed out.
when the communication watchdog timer is
satisfied by regular communications activity
Example for terminal [11] (default output
configuration shown – see
Inverter output
terminal circuit
Example for terminal [AL0], [AL1], [AL2] (requires
output configuration – see
Inverter logic
circuit board
AL0
Power
supply
See I/O specs on page 4-6
Description
page 3-54):
NDc
CM2 11
RY
page 4-35 and 3-54):
NDc
AL1 AL2
Load