Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 51)

I/O Communication
Chapter 3
3-3
Table 3.B
NominalĆBlockĆTransfer Times in Milliseconds for a BlockĆtransfer
Instruction
Channels with blockĆ
transfer I/O modules
Number of active channels
transfer I/O modules
1 2 3 4
1 27 27 28 35
2 x 29 30 36
3 x x 31 38
4 x x x 40
4. Count the number of block-transfer I/O modules on the channel. If
the chassis containing a block-transfer I/O module appears more than
once in the I/O chassis scanning list, count the module once each time
the chassis appears in the list.
5. Count the number of entries in the I/O chassis scanning sequence list
for the channel.
6. Calculate the time between block transfers as follows:
T = (NBT x NM)ms + (NE – 1) x 7ms
Where: Is the:
T
time between block transfers
NBT
nominal blockĆtransfer time (Table 3.B)
NM
number of blockĆtransfer modules (step 4)
NE
number of entries in the I/O scan list
PLC-3 family controllers can communicate with other PLC-3 family
controllers using peer-to-peer or backup communication channels.
PeerĆtoĆPeer Communication
A peer-to-peer communication channel includes one PLC-3 or PLC-3/10
controller configured as the master and up to six PLC-3 or PLC-3/10
controllers configured as slaves. The master communicates with all slaves
on the channel, while each slave communicates only with the master
(Figure 3.1).
Also, when configured in a backup system, the backup slave receives all
input data that are sent to the primary slave if the slave numbers are
the same.
PeerĆtoĆPeer and Backup
Communication