6985 datasheet(13/20 Pages) PHOENIX

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IB IL RS 485/422-PRO ...

6985_en_05

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10.5

3964R protocol

This protocol, developed by Siemens, is the most complex.

It uses start and end identification, checksum and time

monitoring.

5 buffers are available for transmitting, 25 buffers are

available for receiving.

The optional 3964 priority defines which device may send

first (high priority) if there is an initialization conflict (several

devices attempting to send data simultaneously).

10.6

XON/XOFF protocol

This protocol operates like the transparent protocol,

however, using a software handshake.

Data transmission with this protocol is controlled by the

XON and XOFF characters. XON is set to 11

hex and XOFF

to 13

hex.

If the terminal receives an XOFF, no more serial data will be

sent until an XON is received.

The terminal itself will transmit an XOFF if the available

space in the receive memory is less than 5 bytes. As soon

as more memory becomes available again, the module will

transmit a single XON.

Transmission of serial data is not filtered. Any characters,

which occur with the code defined for XON and XOFF, are

thus transmitted and may trigger undesirable events at the

receiver. When serial data is received, the XON and XOFF

characters are filtered and are not available as data. Any

characters with the XON or XOFF code are lost. Ensure that

characters with these codes do not appear in the data

stream.

With the XON/XOFF protocol this function is only

completely available for the RS-422 interface. It can be

discussed if using the protocol for the RS-485 interface is

useful as the latter is a half duplex connection, which

enables either to transmit or to receive data. However, with

the XON/XOFF protocol the receiver can respond with a

XOFF at any time when transmitting characters. Reception

of this control character by the transmitter is thus not

ensured.

10.7

Movilink protocol

The terminal is the Movilink master in the Movilink protocol.

After transmission of a telegram the terminal waits for a

maximum of 500 ms for the response. After the response

was received, the response data is available in the input

data. Only then can the next telegram be sent.

A delimiter is placed ahead of the process data when a

Movilink telegram is being sent. The calculated checksum is

added behind the process data.

When the data is received, the delimiter and the checksum

are filtered out before the data is transmitted over the bus.

Transmit or receive errors are reported when a transmission

timeout or a negative checksum comparison occurs.

Transmit and receive buffer have a size of 11 bytes each.

Character delay time:

220 ms

Acknowledgment delay time:

2 s

Block waiting time:

10 s

Number of attempts to establish a connection:

As the RS-485 interface is a half duplex interface

a waiting time (slave response time) is kept

between data transmission and reception. It is

11 bits and depends on the baud rate.

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