Lenze EPM−T9XX Modular system - Manual (Page 181)

Transmitting process data
Process image of the modular system
8
Networking via system bus (CAN)
8.3
8.3.5
L
8.3−7 EDSPM−TXXX−9.0−11/2009
In the I/O system shown in the example, the transmission time of the input signals
at the module M3 (8×digital input) to the master is to be detected. The baud rate
amounts to 500 kbits/s.
Solution:
l For transmitting the input signals, the module assigns one byte (byte 3) of
the process data channel PDO1−Tx.
l 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 ms) ) 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