Mitsubishi MELSEC LJ71C24, User Manual

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APPENDIXES
APPENDIXES
Appendix 1 Buffer Memory
The buffer memory is the memory of the C24 used for storing data sent to or received
from the CPU module. (Setting values, monitor values, etc.)
Initial values are set to the buffer memory.
When changing the initial values, set the parameters in GX Works2 and write them to
the flash ROM.
For details, refer to (3).
(1) Structure of the buffer memory
A buffer memory consists of a user area and a system area, as shown below.
(a) User area
1) This is the area where users write/read data.
2) The user area consists of areas for storing setting values for data
communication, for actual data communication, and for storing
communication status and communication error information.
3) Data read/write to the user area should be performed following the
instructions in the corresponding detailed reference page.
(b) System area
This area is used by the C24 system.
(2) List of buffer memory assignments
A buffer memory is configured with 16 bits per address.
Name, default value, etc. of each address of the buffer memory is shown in the
lists on the following pages.
1) Abbreviations in the Protocol column
MC : MC protocol
Pd : Predefined
protocol
Non : Nonprocedural protocol
Bi : Bidirectional
protocol
2) Meaning of symbols shown in the Protocol column
The following symbols are assigned to protocols related to the setting
values of a corresponding area and to areas used for controlled with user
settings, and indicate what kind of access is allowed to the area in question.
RW : Area where it is possible to read/write from/to the CPU module
and an external device.
R : Area where only reading is possible from the CPU module and an
external device.
– : System area used by the system or area not used by the
corresponding protocol.
3) Meaning of symbols shown in the Registration column
Indicates whether or not it is possible to use a value in the corresponding
area by registering it to the flash ROM of the C24.
Allowed : Area that can be registered and used.
Not allowed : Area that cannot be registered.
App.