Omron EJ1 User Manual page 186

Connecting More Than One HFU
Operation and
Precautions
Refer to 5-1-3 Detailed Settings for information on data linked with the
PLC. Be sure that the areas of PLC memory used by the different HFUs do
not overlap.
INCORRECT
PLC Memory
HFU No. 0
Upload area
HFU No. 1
Upload area
■ Read/Write Period for PLC Memory
When more than one HFU is connected, communications will be performed in
the following order according to communications unit numbers. The read/write
period for PLC memory will thus be relatively long in comparison to the read/
write period for a 1:1 connection.
0 1 2 ... Max. communication unit number
Or, 32 33 34 ... Max. communication unit number
■ Startup
When more than one HFU is connected, the HFU with communications unit
number 0 is the master for the EJ1. If using a version
32 is the master for the EJ1.
Other HFUs will start communications after the master starts communica-
tions. Be sure to turn ON the power to the master HFU first.
For HFUs that are not the master, communications will start even if the power
is not turned ON. If the power to an HFU is not ON, communications standby
time will occur, and so communications will increase in length by the time
required for one cycle of communications with all Units.
■ Power Interruptions
If power is interrupted to one HFU, communications will still continue for the
other HFUs. A communications standby time will occur for the HFU that does
not have power, and so communications will increase in length by the time
required for one cycle of communications with all Units.
The operation of the HFU after power is restored is different for the master
HFU and other HFUs.
Master HFU A programless link error may occur depending on when the master
HFU is started. If the Selection of Programless Communications
Operation during Error parameter is set to continue operation, then
communications will recover automatically after power is restored.
Other HFUs Communications will recover automatically after power is restored.
Section 5-2
CORRECT
PLC Memory
HFU No. 0
Upload area
HFU No. 1
Upload area
0 1 ...
32 33 ...
Unit, unit number
V1.2
V1.2
161