Diagnostic Status Led's (S1, S2, S3, S4); Rs485 Connections - Novatech Bitronics M87X Series Manual

snapping the ferrite closed. Tie RS-485 cable shields (pin 5) to earth ground at one point
in system.
The recommended torque rating for the terminal block wire fasteners on ports P2-P4 is 2.2
In-Lbs, 0.25 N-m.
3.1.1c Diagnostic Status LED's (S1, S2, S3, S4)
There are four LED's on the front panel: S1, S2, S3, and S4. They perform the following
functions:
LED Description
S1
On while flash memory is being written to, otherwise off.
S2
Flashes every 5 power-line cycles, indicates DSP operating properly.
S3
On while CPU is busy. Intensity indicates CPU utilization level.
S4
On during internal self-diagnostics after boot-up.
3.1.1d RS485 Connections
Note that various protocols and services have different port connection requirements.
When making connections to serial ports for Modbus or DNP3 over RS485, 2-wire half
duplex is required. This is because it is necessary to maintain a minimum time period (3
1/3 characters) from the time the transmitter shuts off to the next message on the bus in
order to guarantee reliable communications. However, when using Zmodem or connecting
to the remote display, asynchronous 2 way communications are required, and therefore a
4-wire full duplex (technically RS422) connection is needed. See figures 4 and 6 below
for RS485 cable wiring and signal assignment diagrams showing both 2 and 4 wire.
There are special considerations for multi-drop Zmodem connections. Zmodem protocol
was developed for RS232 point-to-point connections so it does not support any standard
convention for addressing. Therefore, it does not facilitate multi-drop communications
buses. In order to make it possible to use one modem to establish remote
communications with multiple 70 Series devices when the Ethernet option (preferred) is
not fitted, the following proprietary convention is employed.
When using HyperTerminal or a dial-up modem with RS485, the port on the IED must be
configured for "Zmodem" protocol, not for "Zmodem/Display/Log". This is done with the
pull-down menu in the Configurator program, see illustration below. Selecting Zmodem
also enables an address to be set for the selected COM port. When daisy-chaining
multiple devices on RS485, each device must have a unique address.
ML0021 August 15, 2018
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