Siemens SIMATIC TIWAY 1 Manual de usuario descargar pdf (Pagina 196)

USING THE BDLC PROTOCOL

UNILINK HOST

ADAPTERB–11

USER MANUAL

B.5.4 BCS

Err

When

the Block Checksum calculated by the receiver does not match the BCS in

the I-Frame, the receiving station completely ignores the message. This is

because with an incorrect checksum, there is no guarantee that the address

field contains the correct address. Recovery is then initiated by the sending

station

when the timeout period expires.

B.5.5 T

imeout Err

ors

The

adapter should always respond to a

host computer BDLC command within

30 ms. If it does not, the host computer should try to retransmit the

unacknowledged I-Frames. Timeouts are caused by receiving a frame with a

BCS error, in which case the adapter does nothing, and by the adapter going

offline

(no power or host port media is disconnected).

B.5.6

RR and REJ Recovery

When the sending station receives

an RR or REJ with an N(R) sequence count

less than its internal send count, it should retransmit the unacknowledged

I-Frames.

1 2 ... 191 192 193 194 195 196 197 198 199 200 201 ... 207 208

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Siemens SIMATIC TIWAY 1 Manual de usuario Pagina 196