Message Communications Performance - Omron K3HB - MANUAL 2 Manual

Message Communications Performance

Sample Program
Note
6-2 Message Communications Performance
6-2-1 Message Communications Time
Note
8-6
The times described above are required for the DeviceNet system to start.
The sample program in this section shows how to use the Master Slave Sta-
tus to skip slave I/O processing until remote I/O communications have started.
Refer to the operation manual for the Master Unit for information on the Mas-
ter Status Area.
The following conditions apply to this sample program.
PLC: CS1 Series
Master Unit's unit number: 00
2001 2001
15 14
I/O Data
Communications
Error/Error
Flag
Communications
Stop Flag
The message communications time is the time required from when the Master
Unit starts to send a message on the network until the entire message has
been sent when a message is being sent from one node to another. The mes-
sage will consist of data for a SEND or RECV instruction and a FINS com-
mand for an IOWR or CMND instruction.
If another message is sent before the message communications time elapses
or is a message is received from another node before the message communi-
cations time elapses, the response message being sent or the message being
received may be corrupted. When performing message communications it is
thus necessary to allow the message communications time to elapse before
performing message communications again using SEND, RECV, CMND, or
IOWR instructions and to allow the message communications time to elapse
between sending messages to the same node. If a send or receive message
is corrupted, a record will be stored in the error log in the Master Unit. Use a
FINS command to read the error record or use the Configurator to monitor the
error log.
The message communications time can be estimated using the following
equation:
Message communications time = Communications cycle time x {(number of
message bytes + 15) ÷ 6 + 1}
The number of message bytes in the number of bytes after the FINS com-
mand code. The communications cycle time will depend on whether remote
I/O communications is being used and can be calculated as described next.
(004)
JMP #0001
Slave I/O
processing
(005)
JME #0001
Section 6-2