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DVP-ES2/EX2/SS2/SA2/SX2/SE Operation Manual - Programming
1-4
1.4 PLC Registers and Relays
Introduction to the basic internal devices in a PLC
X
(Input Relay)
Bit memory represents the physical input points and receives external input
signals.
Device indication: Indicated as X and numbered in octal, e.g. X0~X7,
X10~X17…X377
Y
(Output Relay)
Bit memory represents the physical output points and saves the status to be
refreshed to physical output devices.
Device indication: Indicated as Y and numbered in octal, e.g. Y0~Y7,
Y10~Y17. ..Y377
M
(Internal Relay)
Bit memory indicates PLC status.
Device indication: Indicated as M and numbered in decimal, e.g. M0, M1,
M2…M4095
S
(Step Relay)
Bit memory indicates PLC status in Step Function Control (SFC) mode. If no
STL instruction is applied in program, step point S can be used as an internal
relay M as well as an annunciator.
Device indication: Indicated as S and numbered in decimal, e.g. S0, S1,
S2…S1023
T
(Relay)
(Word)
(Dword)
Bit, word or double word memory used for timing
and has coil, contact and
register in it. When its coil is ON and the set time is reached, the associated
contact will be energized. Every timer has its resolution (unit:
1ms/10ms/100ms).
Device indication: Indicated as T and numbered in decimal, e.g. T0, T1,
T2…T255
C
(Counter)
(Relay)
(Word)
(Dword)
Bit, word or double word memory used for counting and has coil, contact and
register in it. The counter count once (1 pulse) when the coil goes from OFF to
ON. When the predefined counter value is reached, the associated contact will
be energized. There are 16-bit and 32-bit high-speed counters available for
users.
Device indication: Indicated as C and numbered in decimal, e.g. C0, C1,
C2…C255
D
(Data register)
(Word)
Word memory stores values and parameters for data operations. Every
register is able to store a word (16-bit binary value). A double word will occupy
2 consecutive data registers.
Device indication: Indicated as D and numbered in decimal, e.g. D0, D1,
D2…D4999
E, F
(Index register)
(Word)
Word memory used as a modifier to indicate a specified device (word and
double word) by defining an offset. Index registers not used as a modifier can
be used as general purpose register.
Device indication: indicated as E0 ~ E7 and F0 ~ F7.