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7.3.1
Communication Condition s and Restrictions Relating to Functions
Precautions when Using the FP2 CPU Unit <1>
If the processing of commands and responses sent from a host computer or display panel extends over
multiple frames, a busy error (error code 53) will be returned to other ports if communication is currently
being carried out on one port, and communication will be inhibited on those other ports. Combinations to
which this restriction applies are shown in the diagram below.
Group A ….. Group comprising the tool port of the CPU unit and the COM. 1 port of Multi
Communication Unit (MCU)
Group B ….. Group comprising the COM port of the CPU unit and the COM. 2 port of Multi
Communication Unit (MCU)
A similar restriction also applies if access is being made from another station connected with the link unit.
Key Point:
“Multiple frames” means that, if a command or response exceeds 118 bytes, the command or response
is divided into multiple segments and transmitted or received.
For example, this applies in cases such as when a program is read from a tool port, when commands,
which continuously read multiple data, are transmitted from a host side.
If using the FP2SH CPU unit, the above restriction does not apply.
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