18 • XM678D I&O Manual 026-1219 Rev 3
9.1.1. RS485 Connection
Sharing a single pressure transducer across multiple
controllers on a LAN:
The parameter (Adr) also defines the number of
configurations on the RS485 network (besides the
LAn); its value must be only from 1 to the total
number of devices present on the RS485 and the LAN
networks.
9.2. How to Enable a
Pressure Probe to
Share Across the LAN
1. Enter the Pr1 level. Follow the steps in Section 12,
How to Program the Parameters (Pr1 and Pr2).
2. Select Pr2 parameter and press the SET key.
3. The PAS flashing message will display, followed
shortly by “0 --” with a flashing zero.
4. Use the up arrow or down arrow button to input the
security code in the flashing digit. Confirm the
security code by pressing SET. The security code is
321.
5. If the security code is correct, the access to Pr2 is
enabled by pressing SET on the last digit.
6. Navigate to the LPP of the Master device (the
device where the pressure probe is connected) and
select (Y). Set the LPP to (N) for all other slave
devices.
7. Navigate to tPP of the Master device and set it to
PP (Pressure Probe). The slave devices tPP
parameter will be set to LAn.
8. Navigate to P5C parameter (Pressure Probe will
always be assigned to P5C) of the Master device
and set it to Pressure Probe type. The slave devices
P5C parameter will be set to nP (No Probe).
Figure 9-1 - Sharing a Pressure Transducer Between Devices on
LAN
CAUTION! Do not connect the RS485 cable to
all the instruments that are already connected
on the LAN - only connect the RS485 to the
master device of the LAN.
CAUTION! The same value of the Adr
parameter in different controllers creates
malfunctioning in the monitoring system or
problems on the synchronized defrosts.
LAN LAN
Shielded Serial Cable
NOTE: If pressure is not being shared across
the LAN, each XM678D will need its own
Pressure Transducer. Please reference Figure
8-1.
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