6-2
6.1 Overview of Func ation
6.1.1 What is General-purpose Serial Communication
• In general-purpose serial communication, data is sent and received over the COM ports to and from
an external device such as an image processing device or a bar code reader.
• Data is read from and written to an external device connected to the COM port by means of a ladder
program of the CPU unit.
Outline of operation
To send data to and receive it from an external device using the general-purpose serial communication
function, the data transmission and data reception functions described below are used. The F159
(MTRN) instruction and the F161 (MRCV) instruction are used in these operations, to transfer data
between the FPΣ and an external device.
Sending data
Data to be transmitted is stored in the register used as the send buffer. When F159 (MTRN) is executed,
the data is output from the COM port.
• The start and end code specified for the
memory switch in the communication setting
is automatically added to the data that has
been sent.
• The maximum volume of data that can be
sent by MCU is 2048 bytes including the
start and end code.
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