Mitsubishi Electric MELSEC iQ-R Series User Manual page 73

Variable Length
The following shows the details on the variable length setting for each selected data type.
■"LIST" is selected
The following table shows the operations when "LIST" is selected for "Data Type" and the checkbox of "Variable Length" is
selected:
Message type
Sending message
Reception message
■An item other than "LIST" is selected
When an item other than "LIST"
are available to specify the number of units of data: compatibility mode and extended mode.
*1 Excluding ASCII and JIS8.
Specify the number of units of data in the extended mode when sending items with 65535 or more units of data.
The compatibility mode and extended mode are automatically switched according to the number of units of data in a received
item at the time of receiving.
The following table shows the methods for specifying the number of units of data in the compatibility mode and extended
mode.
Item
Number of words in the start area of a control
register
Contents stored in the start area of a control
register
Number of units of data when sending an item
Number of units of data when receiving an item
*2 The upper limit of the number of units of data that can be sent and received differs depending on the data type.
For details, refer to the following:
Page 70 Data types (item format codes)
■Compatibility mode (when the start value of the control register is 0 to 65534)
Ex.
Data type: U2 (2-byte integer (unsigned))
Control register: D0
Value of D0: 3 (0x0003)
Data to send and receive: 0x0123, 0x4567, 0x89AB (3 words)
D0 0x0003
D1
0x0123
D2 0x4567
D3 0x89AB
(1) Number of units of data to send and receive
(2) Data to send and receive
Operation
Refers to the control register, and then determines the list quantity.
Example:
When the list structure was defined by 10 items by the message definition, and the value of the register referenced for
the list quantity is "6" during sending, data of 6 items is sent.
Registers the quantity of the received item data to the control register.
Example:
When the list structure was defined by 10 items by the message definition, and data of 7 items was received during
reception, "7" is registered to the control register.
*1
is selected for "Data Type" and the checkbox of "Variable Length" is selected, two methods
Compatibility mode
1 word
Number of units of data to send and receive (1
word)
*2
0 to 65534 (0x0000 to 0xFFFE)
*2
0 to 65534 (0x0000 to 0xFFFE)
(1)
(2)
Extended mode
3 words
Identifier (65535 (0xFFFF)) (1 word)
Number of units of data to send and receive (2
words)
0 to 262144
(0x00000000 to 0x00040000)
65535 to 262144
(0x0000FFFF to 0x00040000)
7 BASIC FUNCTIONS
7.4 Transaction List
7
71