Siemens SIMATIC TIWAY 1 Manual de usuario descargar pdf (Pagina 201)

USING THE BDLC PROTOCOL

UNILINK HOST

ADAPTER B–16

USER MANUAL

B.7 BLOCK CHECKSUM GENERATION AND CHECKING

calculate the BCS:

Zero both BCS field bytes.

Begin with the address field byte.

3. Add the byte to the most significant BCS byte including any carry bit

generated.

(Use only eight bit arithmetic in these steps).

4. Add the most significant BCS byte to the least significant BCS byte,

again

including the carry

5. Get the next frame byte and go to Step 3. If there are no more bytes,

continue

with the following steps.

Add the least significant byte to the most significant byte.

Calculate the ones-complement of the most significant BCS byte.

Example B–3 illustrates how to calculate the BCS on an example frame. The

BCS like the Cyclic Redundancy Checksum (CRC) detects burst errors,

single-bit

errors, and most double-bit errors.

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Siemens SIMATIC TIWAY 1 Manual de usuario Pagina 201