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7.1 Devices Registers
Broadly two types of registers are present in PLC register database:
1. Internal PLC Registers: Implemented through buffers present in RAM of Base module.
Data Registers (D).
Auxiliary Registers (BW/B).
System Registers (SW).
System coil (S).
Timer Registers (T).
Counter Registers (C).
Base module configuration Registers (MW/M) (Coils and registers are mapped)
I/O Registers of Base Module (XW/X, YW/Y) (Coils and registers are mapped)
Timer devices (T.)
Counter devices (C.)
2. Expansion and Serial I/O Registers: These are external to the unit and can be accessed by communicating with
external module over SPI or serial:
I/O Registers of expansion module and serial module (XW/X, YW/Y).
Configuration Registers (MW/M).
XW, YW, MW, X, Y, M register types of both the register types; viz: base, expansion and serial are encoded with the
following addressing scheme:
XWssrr
YWssrr
MWssrr
ss: Slot Number
rr: register number in slot ss
Xssccc
Yssccc
Mssccc
ss: Slot Number
ccc: coil number in slot ss
Note:
“0” (Zero) is the slot number of CPU module.