Message Communication; Iowr - Omron C200HW-PRM21 Operation Manuals

Message communication

6-1

Message communication

Mailboxes
Control words

IOWR

IORD
6-2

IOWR

74
The Unit handles the message communication via the Input and Output
mailbox. These mailboxes are described in section 5-2.
The control words (see 5-3-1) can be used to send standard messages, i.e.
PROFIBUS control commands. The IOWR instruction can be used to send
any fieldbus-specific message. The advantage of this method is that the Unit
will be able to handle future upgrades of fieldbus message types.
The Input mailbox will contain responses to commands sent out via the
Output mailbox. The Unit will automatically remove responses to control
commands as they do not contain any valuable information. Responses to
other commands sent with the IOWR instruction, have to be read with an
IORD instruction to prevent filling up of the Input mailbox.
The transfer of messages via the control words is described in section 5-3-1.
This section will describe the transfer of messages via IOWR / IORD.
Note The transfer of messages with IOWR and IORD is only supported by the
C200HE, C200HG, C200HX and CS1 PLC's, not by the C200HS.
The ladder symbols for IOWR are shown below.
C Control code
value: #0000
S First source word
value: The address of the first word of the PLC data area that contains the
message to be transferred to the Output mailbox.
D
Destination information
value: Combination of the Unit number of the Master Unit and the message
length (number of words in BCD).
IOWR (-)
C
S
D
Message length (001 ~ 128)
Section 6-1
@IOWR (-)
C
S
D
Unit number (0 ~ F)