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4 DATA COMMUNICATION USING BIDIRECTIONAL PROTOCOL
4.1 Receiving Data from Target Device
Receive area, receive data arrangement and contents
This section shows the receive area and the receive data arrangement for performing data reception using the bidirectional
protocol.
Receive area
The receive area is a memory that stores the data length (receive data quantity) and data portion received from a target
device.
By default, the receive area is assigned to the addresses, Un\G1536 to 2047 (CH1 side) and Un\G2560 to 3071 (CH2 side).
The position and size of the receive area in the buffer memory can be changed with Engineering tool in accordance with the
specifications of the target device and the receive data length. (Page 422 PARAMETER SETTING)
Navigation window [Parameter] [Module Information] "Module Name" [Module Parameter] "Basic Settings"
"Various control specification"
Configure the settings as follows:
• Designate the start address for the area to be used as receive area in the user setting area (Un\G1024 to 6911, Un\G9728
to 16383) to "Receiving buffer memory start address designation".
• Designate the length of area to be used as the receive area in the user setting area (Un\G1024 to 6911, Un\G9728 to
16383) by address count (0001H to 1A00H) to "Receiving buffer memory size specification".
When changing the position and size of the receive area in the buffer memory, if any of the functions below are used
concurrently, make sure that the addresses of the receive area do not overlap with the buffer memory addresses assigned for
storing send/receive data with the functions.
• MC protocol buffer memory read/write function
• MC protocol on-demand function
• Predefined protocol function (Send/receive data storage area)
• Nonprocedural protocol transmission/receive function
• Bidirectional protocol transmission/receive function
• Send/receive data monitoring function
Set the amount of data per data transmission from the target device to C24 to be smaller than the size of the receive data
storage area in the buffer memory.
• (Receive data storage area) (Amount of data in any data portion to be transmitted from the target device)
To transmit data whose size is larger than the receive data storage area, increase the receive area, or divide the send data
before sending.
The position and size of the receive area can be changed in the buffer memory.
• 'Receiving buffer memory start address designation' (Un\G166/326)
• 'Receive buffer memory length designation' (Un\G167/327)
The units of data length (word/byte) is in accordance
with the word/byte units designation with Engineering tool.
CH1
address
Buffer memory
Receive data count
Reception area
Data length
The contents of data length of the received message are stored.
Received data
Data portion
The contents of the data area of received
message are stored in ascending address order.
(Default)
Un\G1536
Un\G1537
Un\G2047
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