BECKHOFF BK7300 - Manual (Page 16)

Basic information
12 BK7300
Data consistency
Items of data are said to be consistent if their content all belongs together,
and if they are transmitted as a single block. Examples of data items that
belong together are: 1. the high and low bytes of an analogue value (word
consistency), and 2. a control/status byte and the associated parameter
word for access to the registers. Data consistency in the interaction of
peripheral devices and their controllers is, in a basic sense, only assured
for a single byte. In other words, the bits of a byte are read in or written
together. Byte consistency is sufficient for handling digital signals.
Whenever values have a length of more than 8 bits, analogue values for
instance, the consistency must be extended. The different bus systems
guarantee consistency up to the required length. Correct transfer of the
consistent data from the bus system master to the controller is important.
The corresponding manual for the bus system will provide a detailed
description of the correct procedure, in particular the description of the
used master interfaces. Those chapters of this manual that deal with the
fieldbus refer to the most widespread interfaces.
Processing complex signals All byte-oriented signal channels such as RS232, RS485 and incremental
encoder, can use byte lengths greater than two. Apart from the actual
difference in length, the procedure is always comparable with that for
analog signals
Preparing for Operation and Diagnostics
After switching on, the bus coupler immediately checks the connected
configuration. Error-free start-up is signaled by extinction of the red LED
“I/O ERR“. If the “I/O ERR” LED blinks, an error in the area of the terminals
is indicated. The error code can be determined from the frequency and
number of blinks. This permits rapid rectification of the error.
The diagnostic LEDs The bus coupler has two groups of LEDs for the display of status. The
upper group with four LEDs indicates the status of the respective field bus.
The significance of the “field bus status“ LED is explained in the relevant
sections of this manual - it conforms to conventional field bus displays.
On the upper right hand side of the bus couplers are two more green LEDs
that indicate the supply voltage. The left hand LED indicates the 24 V
supply of the bus coupler. The right hand LED signals the supply to the
power contacts.
Local errors Two LEDs, the “I/O” LEDs, in the area below the field bus status LEDs
referred to above, serve to indicate the operating status of the bus
terminals and the connections to these terminals. The green LED lights up
in order to indicate fault-free operation. The red LED blinks with two
different frequencies in order to indicate an error. The error is encoded in
the blinks as follows:
Fast blinking Start of the error code
First slow sequence Error code
Blink code
Second slow sequence Error code argument
Start of the error code Error type Error location