Omron CP1L-EL20DR-D, Operation Manual

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Appendix K
Ethernet Specifications
Usage Note
Item Specification Description
Data length of FINS
message 1004 bytes (max) The max data length of FINS message can be dealt with by PLC’s
FINS service.
This data length does not include FINS header whose length is 12
bytes, so the max length of FINS message is 1016 bytes.
FINS buffer size 16K bytes The FINS buffers combine with 8 groups, and each group
includes 1K bytes receive buffer and 1K bytes send buffer.
When FINS message wants to be dealt with by PLC's FINS ser-
vice, it should be saved into FINS buffer.
So in one PLC’s cycle, there are max 8 FINS message can be
dealt. The FINS message is sent from Ethernet host, or CMND/
SEND/RECV instructions.
Driver buffer number Input: 55×592 bytes
Output: 55×592 bytes
When PLC receives an Ethernet packet, it is saved into input
buffer.
The packet whose length is not larger than 592 bytes uses one
input buffer, and the packet whose length is from 593 bytes to
1184 bytes uses two input buffers.
So input buffer can save 55 Ethernet packets whose lengths are
all not larger than 592 bytes at one time, and can save 27 max
length FINS message which uses tow input buffers at one time.
Output buffers are used at Ethernet send process.
Process of driver
buffer overflow The last packet will be
dropped. When PLC's driver input buffer is overflow, only the last packet will
be dropped and other packets will be dealt with.
So the communication can recover to normal state quickly.
Connection number
(FINS/TCP) 3 for user1 for CX-Programmer
auto connection There are 3 FINS/TCP connections applied to customer, and all of
them can be set to FINS/TCP client or FINS/TCP server.
Except the above 3 FINS/TCP connections, there is a FINS/TCP
connection reserved for auto connection with CX-Programmer, so
customer cannot change its setup and only can use it for auto
connection with CX-Programmer.
Item Usage Note
FINS buffer size Because there are 8 FINS message be dealt with at the same time, it is better not to send more
than 8 FINS commands not only from Ethernet host bus also from CMND/SEND/RECV instruc-
tions at one time.
For example, if there are 16 FINS commands to be sent, it is better to send these commands by
twice and each time to send 8 FINS commands. After the first 8 commands finish, to send the sec-
ond 8 commands.
It is possible to send 16 FINS commands at one time, but only 8 FINS commands can be dealt with
at once and others are saved in driver input buffer.
Driver buffer number If PLC receives many Ethernet packets that arouses driver input buffer overflow, the last packet will
be dropped. If the dropped packet is FINS message, the FINS communication will be pause.
It can be used to calculate the Ethernet storm which can be endured by PLC. How many duty pack-
ets, such as broadcast packets, can be included in one Ethernet storm.