Omron CJ - REFERENCE MANUAL 02-2010 Reference Manual page 934

3. Instructions
Note 1 If you use communications instructions inside interrupt tasks (regardless of whether you specify communications
ports or use automatic port allocation), use the DI and EI instructions to prohibit executing interrupt tasks when exe-
cuting communications instructions with automatic port allocation in cyclic tasks, as shown below.
Cyclic Task
a (Executing)
a (Executing) c (Standby)
2 If it is possible that more than eight communications instructions will be executed at the same time, always check to
be sure there is an available communications port before executing a communications instruction, even when using
automatic port allocation.
Execution
condition
A202.15
d (Execution
completed)
898
DI
@Communications
instruction
Port: F
@MOV
A218
If there are communications instructions in any
b (Port)
interrupt tasks, prohibit execution of interrupt
tasks between DI and EI instructions.
@MOVL
A216
e (Code storage
location)
c (Standby)
EI
TST
A214
b (Port)
,IR0
#0000
Use A202.15 (Communications Port Allocation Enabled Flag) and
execute communications only when a communications port is available.
KEEP
a (Executing)
d (Execution completed)
MOVL
e (Code storage
location)
IR0
Network communications
error processing
CS/CJ/NSJ Series Instructions Reference Manual (W474)