Image Processing Reference
In-Depth Information
Communication cycle
RT channel
IP channel
Master
......
Slave 1
Slave 2
Slave 3
Time
FIGURE .
SERCOS timing.
time for the high-speed cycle is the cycle of the SYN frame, and the cycle time of the medium-speed
or low-speed cyclic data is a multiple of the SYN frame cycle.
TCnet is able to handle redundant transmission mediums. The RTE-TCnet stack manages the
selection of two redundant inputs of received frames and two outputs to two redundant transmis-
sion mediums. In the case of collision on one of the mediums, the transmission is continued on the
other. he RTE-TCnet accepts the first incoming frame without transmission error from one of the
redundant transmission media. his is the reason why in Table . the recovery time is set to .
The RTE-TCnet Application Layer Service defines the common memory system. The common
memory is a virtual memory shared over the RTE-TCnet network by the participating application
processes running on each node. he common memory is divided into numbers of blocks with dif-
ferentsizes.Onenodeisthepublisherofablockofdataandbroadcaststhisdatablocktoallthe
others by means of cyclic data service. Each node receives the data block as a subscriber and updates
its local copy of the common memory. By this means, each controller can quickly access each other's
data by accessing its local copy of the common memory.
21.4.2.3 EPA (Profiles 14/1 and 14/2)
he EPA
∗
protocol (Ethernet for Plant Automation) profile is a Chinese proposal.
TABLE .
Performance Indicators for TCnet
Performance Indicator
Profile /
a
Profile /
b
Delivery time
ms/ ms/ ms
ms/ ms/ ms
Number of end-stations
Number of switches between end-stations
( Repeater)
( Repeaters)
Throughput RTE
././. M octets/s
././. M octets/s
Non-RTE bandwidth
%
<
%
Time synchronization accuracy
—
—
Non-time-based synchronization accuracy
<
µs
<
µs
Redundancyrecoverytime
s
ms
a
With no non-RTE bandwidth.
b
With allocated non-RTE bandwidth.
∗
EPA is the trade name of Zhejiang SUPCON Co. Ltd.
