Image Processing Reference
In-Depth Information
Default
communication
parameter
Default
mapping
parameter
Change
polarity
Filter
mask
1400
h
6202
h
1600
h
6208
h
1
2
3
4
5
6
7
Entry
into
6200
h
Receive
RPDO1
Change
polarity
Block
filter
MAP from
RPDO1
Reception
from
CAN
Digital
output
(single)
Select
mode
Device
failure
6206
h
Error
mode
6207
h
Error
value
FIGURE .
Conceptual architecture of digital outputs.
The actual transmission on the CAN bus () is driven by the trigger block. By default, the asyn-
chronous mode is enabled, that triggers the transmission as soon as any of the input channels changes
its logical value. However, this behavior can be changed through objects
h
,
h
,and
h
.
Moreover, triggering can be globally enabled/disabled through the (Boolean) object
h
.
It is clear that, by writing into the relevant entries of the OD, a control application or a configuration
tool can easily customize the behavior of each single digital input channel, as well as decide how these
information are sent over the CAN network.
15.7.2.2 Digital Output Devices
Figure . shows the steps involved in the processing chain affecting the operation of a digital output
device. Frames received from the CAN bus () are first filtered according to the information stored in
the RPDO communication parameter (). Whenever the received frame corresponds to the RPDO
configured for the device, its payload is decoded according to the PDO mapping parameters, and
the related values are stored () in the suitable entry of the OD (object
h
). After an optional
polarity change (), configured through the object
h
, the output value is made available on the
related output channel (). A filter block is also provided () through object
h
:whendisabled,
the previous value is retained on the output channel.
The lower part of Figure . describes the behavior of the actuator in the case a device internal
failure (including heartbeat or life guarding events) is detected. In order to improve safety, two objects
(
h
and
h
) are provided that specify the value each digital output channel should assume in
thecaseofdevicefailure.Inparticular,eachoutputcanbesetseparatelyto,,oritsownvaluebefore
the failure was detected. Whenever a failure is detected, the output is automatically switched () to
such a value.
References
[PRO] Barranco M., Proenza J., Rodriguez-Navas G., and Almeida L., An active star topology for
improving fault confinement in CAN networks,
IEEE Transactions on Industrial Informatics
,
(), -, May .
