Omron SYSMAC CJ - REFERENCE MANUAL 08-2008

1031
Network Instructions Section 3-25
Communications Flags The operation of the communications flags is outlined below.
• The Communications Port Enabled Flag is reset to 0 when communica-
tions are in progress and set to 1 when communications are completed
(normally or not).
• The status of the Communications Port Error Flag is maintained until the
next time that data is transmitted or received.
• The Communications Port Error Flag will be reset to 0 the next time that
data is transmitted or received, even if there was an error in the previous
operation.
About Communications
Port Numbers
There are 8 logical communications ports provided, so 8 communications
instructions can be executed simultaneously. Only one instruction can be exe-
cuted at a time for each communications port. Exclusive control must be used
when more than 8 instructions are executed.
These 8 communications port numbers are shared by the network instructions
(SEND(090), RECV(098), and CMND(490)), the serial communications
instructions (TXDU(256) and RXDU(255)), and the PROTOCOL MACRO
instruction (PMCR(260)). Be sure not to specify the same port number on two
instructions at the same time.
0204
Busy
C
ommunications Port
Enabled Flag
Network instruction
(
SEND, RECV, or CMND)
C
ommunications Port
Error Flag
C
ommunications Port
C
ompletion Code
Instruction 1
executing
Previous
com
p
letion
0000 (Normal
completion)
Instruction 2
executing
Instruction 3
executing
0000 (Normal completion)
Controller Link Unit,
Ethernet Unit, or Serial
Communications Unit
Port
CPU Unit
Instruction 1
Instruction 2
Instruction 3
Instruction 4
Instruction 5
Instruction 6
Instruction 7
Instruction 8