Beckhoff C1220 Manual de usuario descargar pdf (Pagina 24)

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Software description of functions 24

Beckhoff Lightbus - PC interface card C1220

Structure of the buffer for string communication

Transmit / receive buffer Description

0x00.0

Active flag

0x00.1 - 0x00.7

Error field 0x00: String transmitted without error.

0x04: Optical fibre error.

0x08: String slave not initialised.

0x10: String slave not yet ready for

communication.

0x20: Timeout during string transmission.

0x40: String length error.

0x01

Empty

0x02

Address of the sender (TX)

0x03

Address of the receiver (RX)

0x04

Channel / priority

0x05

String length

0x06 - 0xFF

String data

Sending a string

To send a string to a string slave, the string data (header and user data)

are placed in the C1220’s transmit buffer. If the active flag is now set, the

master card is induced to send the string. Once this has occurred, the

master card now resets the active flag. If any error has occurred during the

string transmission, this is indicated in the error field.

Receiving a string

If a string is received from a string slave, it is placed in the C1220’s receive

buffer, and the active flag is set. As long as a string that has been received

has not been acknowledged by resetting the active flag, no further string

will be fetched from a string slave.

Slave to slave string communication

Slave to slave communication (received string has RX not equal to “0”) is

processed entirely by the master card.

String communication can be used to access the register interface of a bus

coupler or of a terminal in a simple manner.

To trigger register communication, channel 8 must simply be entered into

the string header. In the string data area an additional header, 6 bytes

large, is necessary.

High Byte Low Byte I/O

Address

127

5 User data

Number of words Register (base) 4

R/W Table Terminal number 3 Header for register communication

Message Ident 2

Size Priority 8 1

RX_address TX_address 0 Header for string communication

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 30

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Beckhoff C1220 Manual de usuario Pagina 24

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