Hitachi Vector Control with the SJ300 Inverter Application Note page 20

(5-2) How many slaves can be connected?
There are two ways of connecting slave SJ300 to one master SJ300.
(5-2-1) Parallel connection
Maximum 10 slaves can be connected to a master based on RS422B EIAJ US. Actual capability is 32 units.
In this case, every slave follows the master with a minimum delay.
Driver
(Master)
Fig 13-1. Parallel connection of Master-Slave control
s
RS422 standard
Load impedance of the driver
Input impedance of the receiver
s
Actual spec of SJ-FB
Load impedance of the driver
Input impedance of the receiver
(5-2-2) Series connection
Any numbers of slaves can be connected to a master theoretically.
Delay in response will be bigger at far end.
Driver
(Master)
Delay 1
Total delay
= 1
Fig 13-2. Series connection of Master-Slave control
© 2002 Hitachi America, Ltd.
Receiver (Slave)
R
L
1
R
i1
Receiver (Slave)
R
L
1
Delay 2
Total delay
2
R
i2
R > 100
L
R > 4 k
in
R > 100
L
R = 12 k
in
Termination resistor R
Make it ON for every unit
2
Total delay
= 1+ 2
20
Termination resistor R
Make it ON only at the furthest place
150
32
R
i32
In case of 32 slaves with SJ300;
k / 32) // R
RL = (12
= 107 > 100
Capability is 32 units
(Internal)
T
Delay 3 Delay n
Total delay
= 1+ 2+ 3 =
(Internal)
T
.
T
n
n