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
Xssccc
Yssccc
Mssccc
ss: Slot Number
rr:register number in slot ss
ss:Slot Number
ccc: coil number in slot ss
Note:
“0” (Zero) is the slot number of CPU module.
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