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14 ON-DEMAND DATA COMMUNICATIONS USING USER FRAMES
14.2 User Frame On-Demand Data Transmission and Buffer Memory Used
14.2 User Frame On-Demand Data Transmission and
Buffer Memory Used
This section explains the on-demand data transmission processing using a user frame and the arrangement of on-demand
data based on the user frame specification to the buffer memory.
Transmission of on-demand data using user frames
The following describes the transmission of on-demand data using user frames.
■Processing on the CPU module side
• Before issuing a transmission request to C24, set the No. of the user frame registered in C24 to the buffer memory shown
in the table below.
• The execution procedures and control procedures of the CPU module side excluding the above are the same as
transmitting on-demand data without user frame described in the following manual.
( MELSEC Communication Protocol Reference Manual)
■Processing of the target device side
• When the target device receives the user frame transmitted by C24 as the start frame, receive it as on-demand data.
Buffer memory to be used and the order of on-demand data
■Buffer memory to be used
For on-demand data transmission using a user frame, the user frame to be transmitted is designated in the buffer memories
shown below.
*1 Designates the registration No. (shown below) of the user frame to be transmitted from among the user frames registered in C24.
1H to 3E7H (1 to 999) : Default registration frame
3E8H to 4AFH (1000 to 1199) : User frame (registered in flash ROM)
8001H to 801FH (-32767 to -32737) : User frame (registered in buffer memory)
■On-demand data arrangement
The following shows the order of on-demand data by user frame specification.
Address Name Description
CH1 CH2
A9H 149H On-demand user
frame specification
Start frame No. designation (1st) Designates the number of the user frame to be
transmitted as the start frame.
0H : No designation
Others : Designated
*1
For the 1st frame, other than 0 must be designated.
When designating the 1st frame, the 2nd frame can
also be designated.
AAH 14AH (2nd)
ABH 14BH Final frame No. designation (1st) Designates the number of the user frame to be
transmitted as the final frame.
0H : No designation
Others : Designated
*1
When designating the 1st frame, the 2nd frame can
also be designated.
ACH 14CH (2nd)
On-demand data
User frame User frame User frame User frameSend data
Transmitted when last frame (2nd) designated.
Transmitted when last frame (1st) designated.
On-demand instruction/transmitted when send
data designated in buffer memory.
Transmitted when first frame (2nd) designated.
First frame (1st).
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