Transmitting process data
Process image of the modular system
10
Network via CANopen
10.4
10.4.5
l
10.4-7
EDSPM-TXXX-3.0-04/2004
In the I/O system shown in the example, the transmission time of the input signals
atthemoduleM3(8×digital input) to the master are to be detected. The baud rate
amounts to 500 kbits/s.
Solution:
z
For transmitting the input signals, the module assigns one byte (byte 3) of
the process data channel PDO1-Tx.
z
The delay time t
d
within the module amounts to 3 ms.
1. Calculating the time required for copying t
c
into the CAN object directory:
t
c
= 50 ms + 1 ⋅ 25 ms = 75 ms
2. Calculating the transmission time t
t
of the input signals to the fieldbus:
t
t
= 75 ms + (1 ⋅ 8 ms) + (0 ⋅ 2 m s) + 3000 ms + 742 ms = 3825 ms
3. Calculating the transmission time t
CAN
via the fieldbus:
l
L
EPM – T110 1A.10
PW
ER
RD
BA
ADR.
0
1
+
–
DC
24V
X1
DI 8xDC24V
.0
.1
.2
.3
.4
.5
.6
.7
1
2
3
4
5
6
7
8
9
L
10
EPM – T210 1A
t
CAN
epm-t135
t
CAN
=
CAN telegram length
Baud rate
=
111 bits
500 kbits
s
= 222 ms
4. Calculating the total transmission time t:
t = t
t
+ t
CAN
= 3825 ms + 222 ms = 4047 ms = 4.047 ms
Note!
The internal processing times of the controller must also be
considered.
Example
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