Siemens SIMATIC TI505 Manual de servicio descargar pdf (Pagina 40)

Chapter 4: Communications Parameters 37

Bit Writes with Ladder Logic – Models 325 and 330

The Texas Instrument Hostlink Protocol does not permit an external intelligent device to directly alter

the state of a single bit without overwriting the entire byte in which that bit exists. As a result, the

Operator Station will write to a designated register in the PLC, specifying which bit should be set or

cleared. A section of Ladder Logic Programming is necessary to be written to interpret this value in

order to change the appropriate bit. The starting register that Operator Station will write to is

determined by the register entered in the PLC ID field. If a Bit Write register is not entered, the

To set a bit, the bit number will be sent to the Bit Write register. To reset a bit, the bit number

(decimal) + 1000 (decimal) will be sent to the Bit Write register.

Two rungs of ladder logic will be required for each bit write. Each rung will test the specified register

for the expected value from an Operator Station. If the rung is true, the logic will set or rest a

particular bit as required.

PLC ID

The format for the PLC ID for models 325 and 330 will include both the PLC ID and a memory

address.

XX-ACYYY or XX-YYY or XX

Where

XX PLC ID in range 1-90

- PLC ID/memory specifier

AC Optional memory type

YYY Optional starting AC memory address in range 600-677

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Siemens SIMATIC TI505 Manual de servicio Pagina 40