User`s manual

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CHAPTER 10 ON-DEMAND DATA COMMUNICATIONS USING USER FRAMES
10
10.1 User Frame Data Communications Function
CHAPTER 10 ON-DEMAND DATA
COMMUNICATIONS USING USER
FRAMES
During communications between external device and programmable controller CPU using the MC protocol, on-
demand data can be transmitted from the programmable controller CPU to the external device by on-demand function
using user frames.
This chapter explains the transmission of the data specified by the programmable controller CPU using a message
format other than the message formats (A compatible 1C frame formats 1 to 4, QnA compatible 4C frame format 5)
described in the MELSEC Communication Protocol Reference Manual.
10.1 User Frame Data Communications Function
The user frame data communications transmits and receives the first and last parts of a message in the format
selected by the user during data communications between programmable controller CPU and external device via the
Q series C24.
By using the function described in this chapter, on-demand data shown below can be transmitted from the Q series
C24 to an external device.
(Transmitting in QnA compatible 3C frame format 1)
User frame data communications can be carried out by registering (registered by the data code) the message format to
be transmitted by the external device and the message format to be received by the external device according to the
specifications of the external device to the Q series C24 as user frames.
For the illustration above, the Q series C24 transmits the on-demand data as described below.
• User frame sum check code: Calculates the sum check code according to the contents registered in
advance by the user and transmits the result as ASCII code or binary code data.
• Other than user frame sum check code: Transmits data of the code registered in advance by the user. (No
conversion)
• Send data (character area B): This is the data that the sequence program requested for a transmission with
on-demand instruction. The same contents and list as when transmitted without using a user frame
described in the MELSEC Communication Protocol Reference Manual are transmitted by communication
protocol by GX Developer switch setting and word/byte designation.
HL HL HL HL HL HL
S
T
X
E
T
X
Station No.
Network No.
PC No.
Local station No.
Sum check code
Send data
character
area B
Transmitted by user frame.
On-demand data
Frame identifi- cation No.
As shown in the left, the user can sort the data
except for the "Send data" portion.