Contec F&eIT Series User Manual page 58

Frame format
Using the UDP/IP port address 5007h, the F&eIT Protocol is installed in the data section.
The frame structure takes the format described below. Due to the header byte order conventions, the
Ethernet, IP, and UDP are treated as Big Endians; all other entities are treated as Little Endians, for
which controls exerted by an x86 CPU hold priority.
Table 8.7. Frame Structure
Header name
Ethernet Destination Address
section
Source Address
Type Field
IP section IP Ver4 Header
UDP section UDP Header
Identifier
Version
Command
Sequence number
Response ID
Communica
Virtual address
tion
Access size
server
Status
section
Access ID
Remote MAC address
Reserved
Data section
[Description of communications server headers]
(1) Identifier
(2) Version
(3) Command
(4) Sequence no.
(5) Response ID
(6) Virtual address
(7) Access size
(8) Status
(9) Access ID
(10) Remote MAC address
CPU-CA10(FIT)GY, CPU-CA20(FIT)GY
Side
(byte)
6 Remote MAC address
6 Local MAC address
2 Ethernet II
20 Fragment disabled
8 Check sum disabled
2 "SV"
1 Version of the header structure
1 Command and the ACK flag
2 Frame Id
2 Identifies the sender.
4 Specifies a virtual address space.
2 1436 bytes maximum
2 Result of command execution
8 Identifies the Read/Write privilege
6 Specifies a remote MAC address when using
IP multicasting.
6 Reserved for future use
1436 Data area
--- Identifies the frame as a F&eIT Protocol frame.
--- Indicates the frame version.
--- The virtual address access command.
--- A counter that prevents the occurrence of duplicate frames, wherein
the sequence number is incremented each time a packet is
transmitted.
--- When a response-type command is transmitted, the contents of the
response ID are copied to the response ID for the response frame.
--- Specifies the virtual address being accessed, e.g., device information
can be read by specifying the address 0000h.
--- Specifies the size of the data to be accessed, from 1 to a maximum
of 1436 bytes.
--- Stores status information after the command is executed.
--- This is an ID for virtual address access control.
--- When data is read/written using IP Multicast, the MAC address of
the remote device is set in this header. When data is to be sent to all
devices on the network, the value ALL[F] is set in this header.
(For Unicast: "ALL [0]")
8. System Reference
Remarks
51