4 SERIAL COMMUNICATION FB
4.1 M+FX5UCPU-SerialComm_InputOutput
19
4
■Output label
*1 The data storage position in the word device varies depending on the 8-bit/16-bit mode setting.
*2 The number of required word devices varies depending on the 8-bit/16-bit mode setting.
■Public label
*1 Even if a serial communication error occurs in the used communication channel, error completion and error code are not output and the
FB does not stop. Use a user program to detect the error. For serial communication error and serial communication error code, refer to
the following manual.
MELSEC iQ-F FX5 User's Manual (Serial Communication)
FB details
No. Variable name Name Data type Default value Description
(8) o_bENO Execution status Bit OFF ON: The execution command is on.
OFF: The execution command is off.
(9) o_bSendComp Send completion Bit OFF When this bit is ON, it indicates that data sending is
completed.
(10) o_bRecvComp Receive completion Bit OFF When this bit is ON, it indicates that data receiving is
completed.
(11) o_bErr Error completion Bit OFF When this label is on, it indicates that an error has
occurred in the FB.
(12) o_uErrId Error code Word [Unsigned] 0 Stores the error code that occurred in the FB.
(13) o_uRecvDataLength Number of receive
data points
Word [Unsigned] 0 Stores the number of bytes of data received.
(14) o_uRecvData Receive data storage
device
Word [Unsigned] 0 Specify the head address of the device which stores the
received data.
*1*2
No. Variable name Name Data type Range Description
(15) pb_bSerialComErrUndetection Serial communication
error undetection
mode
Bit ON, OFF ON: FB does not detect serial communication error.
*1
OFF: FB detects serial communication error.
Item Description
Available device CPU module FX5U CPU, FX5UC CPU
Engineering tool GX Works3 Version 1.007H or later
Language Ladder diagram
Number of basic steps 713 steps
The number of FB steps integrated in the program varies depending on the CPU module used, the input/output definition, and
the setting options of GX Works3. For the setting options of GX Works3, refer to GX Works3 Operating Manual.
Processing • When i_bEN (Execution command) turns ON, serial data transfer goes into sending/receiving standby state.
• In data sending standby state, this FB sends the send data specified by i_uSendData (Send data storage device) and
i_uSendDataLength (Number of send data points) using non-protocol triggered by the serial data transfer (RS2) instruction
when i_bSendReq (Sending request) turns ON. When sending is completed, o_bSendComp (Sending complete) turns ON.
• In data receiving standby state, when the FB receives the data, the FB writes the number of the received data to
o_uRecvDataLength (Number of receive data points), writes the received data to o_uRecvData (Receive data storage
device) and then o_bRecvComp (Receiving complete) turns ON.
• This FB checks the following input values when started up. If an error occurs, o_bErr (Error completion) turns ON, and
o_uErrId (Error code) stores the error code.
(1) Send/receive channel number
(2) Allowable number of receive data points
(3) Number of send data points (Only when sending request)
• If an error occurs during data communication processing, o_bErr (Error completion) turns ON, and o_uErrId (Error code)
stores the serial communication error code. For error codes, refer to Page 21 Error code. When
pb_bSerialComErrUndetection (Serial communication error undetection mode) is turned ON by a user program, this FB
does not detect serial communication error. Detect serial communication error by a user program.
• When data receiving is suspended and the time-out time elapses, time-out occurs, and then o_bRecvComp (Receiving
complete) turns ON.
FB compilation method Macro type
FB operation Always executed
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