Eaton PROFIBUS-DP EZ204-DP User Manual download pdf (Page 195)

Example circuits

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In the second cycle break contact M7 is open. The series

circuit is opened. The contact M8 is activated from the result

of the first cycle. Now, all the storage locations are either set

or reset in accordance with the series circuit.

If the relay coils were activated, EZ transfers the result to the

contacts. M8 is now open again. No new pulse can be formed

until I1 has opened, since M7 is open for as long as I1 is

closed.

How does the value reach the shift register?

When shift pulse M8 = ON, the state of I2 (VALUE) is

transferred to storage location M1.

If I2 is activated, M1 is set. If I2 is deactivated, M1 is

deactivated via break contact I2.

How is the result shifted?

EZ activates the coils in accordance with the rung and its

result, from top to bottom. M4 assumes the value of M3 (value

0 or 1) before M3 assumes the value of M2. M3 assumes the

value of M2, M2 the value of M1 and M1 the value of I2.

Why are the values not constantly overwritten?

In this example, the coils are controlled only by the S and R

functions, i.e. the values are retained in on or off states even

though the coil is not constantly activated. The state of the coil

changes only if the rung up to the coil is activated. In this

circuit, the marker relay is therefore either set or reset. The

rungs of the coils (storage locations) are only activated via M8

for one cycle. The result of activating the coils is stored in EZ

until a new pulse changes the state of the coils.

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Eaton PROFIBUS-DP EZ204-DP User Manual Page 195