Omron DRT2 SERIES DEVICENET SLAVES - OPERATION MANUAL 04-2008 Operation Manual page 472

Remote I/O Communications Characteristics
Input Slaves, Output
Slaves, or Mixed I/O
Slaves with More than 8
Bytes of I/O
Refresh Time
Master Unit for CV-series
PLCs
Master Unit for CS, CJ,
C200HX/HG/HE (-Z), and
C200HS PLCs
8-1-3 More than One Master in Network
T = T + T
RT OH BYTE-IN
T :
-OH
T :
BYTE-IN
B :
IN
T :
BYTE-OUT
B :
OUT
Baud rate
500 kbps 0.306 ms
250 kbps 0.542 ms
125 kbps 1.014 ms
The number of output bytes (B
of input bytes (B
IN
The refresh time is the time required for I/O data to be exchanged between
the PLC's CPU Unit and the DeviceNet Master Unit. The PLC's cycle time is
increased when a Master Unit is mounted, as shown below.
Note Refer to the PLC's Operation Manual for more details on the refresh time and
the PLC's cycle time.
The PLC's cycle time (CPU Bus Unit servicing) is increased by the amount
shown in the following table when a Master Unit is mounted to the PLC.
Process
CPU Bus Unit servicing
The PLC's cycle time (I/O refreshing) is increased by the amount shown in the
following table when a Master Unit is mounted to the PLC.
Process
I/O refreshing
Note The number of words refreshed is the total number of words in the I/O Area
that are allocated to the Slaves, including any unused words between those
words actually used by the Slaves.
For example, if there are only two Input Slaves with node addresses 1 and 5,
the 5 input words for nodes 1 through 5 would be refreshed even though the
input words for nodes 2, 3, and 4 are unused.
If message communications are being performed, just add the number of
words used in message communications to the above number of words for
whenever messages are being processed.
The following equation shows the communications cycle time (T
there is more than one Master in the Network.
An example for two Master Units is shown here.
× B + T × B
IN BYTE-OUT
The overhead protocol
The input byte transmission time
The number of input bytes
The output byte transmission time
The number of output bytes
T
OH
0.040 ms
0.073 ms
0.139 ms
) for Input Slaves only is 0, and the number
OUT
) for Output Slaves only is 0.
DeviceNet Unit refreshing: 1.1 ms
DeviceNet Unit I/O refreshing:
Using Master Unit for CS, CJ, and C200HX/HG/HE (-Z)
PLCs
1.72 + 0.022 × number of words (ms) (See note.)
Using Master Unit for C200HS PLCs
2.27 + 0.077 × number of words (ms) (See note.)
Section 8-1
[ms]
OUT
T T
BYTE-IN BYTE-OUT
0.036 ms
0.069 ms
0.135 ms
Processing time
Processing time
) when
RM
451