7
WARNING
The
`ENBL'
signal
should
be
connected
to
an
external
emergency
stop
circuit.
Loss
of
this
input
(or
low
input)
causes
the
command
outputs
to
go
to
zero
regardless
of
motion
processing.
This
input
must
be
energized
to
allow
motion.
Fault Protection
The SMC20 provides both hardware and
software fault protection. The hardware
includes two fault protections:
D
Enable – an optically isolated “enable”
input signal must remain ‘On’ if it goes
‘Off’, controller command outputs go to
zero.
D
Internal Watchdog – if the controller’s
processing units fail, the controller
command outputs go to zero.
Wiring the Common System
Connections
Recommendation: Use 14 to 20 AWG
stranded wire; further, if you insert more
than one wire into a screw terminal, twist
the wires together and solder them. For
the common system connections, insert
the wire into the green screw-type
terminal that comes with the SMC20. If
you intend to operate from the internal
isolated DC supply (24 V) on the
SMC20, use its green screw–type
terminal which also comes with the
controller as shown in Figure 2-5.
Figure 2-5. Wiring the Common
System Connections Using the Internal
Isolated Supply
Figure 2-6. Wiring the Common Sys-
tem Connections with a User Power
Supply
Axis Connections
The axis connections provide the link
between the SMC20 and the actuator
(motor/drive amplifier). Each axis
connection has eight input and eight
output digital signals, all optically
isolated. Figure 2-7 locates the axis
connections on the SMC20 front panel.
Figure 2-7. Front Panel Axis
Connections
Pin
No.
Name
Description/
Function
Z32
DO+
Analog output (differ-
ential)
Z30
DO–
enti l)
"
10 VDC full scale
Note 1
Z28
AGND Analog output
(single-ended)
"
10 VDC full scale
Note 1
Z26
SO
Analog output
(single-ended)
"
10 VDC full scale
Note 1
Z24
AGND Analog signal ground
Z22
IN1+
Analog input
(differential) channel
1 Programmable
Z20
IN1–
1. Programmable
usage
"
10 VDC full
scale. See page ##.
Z18
AGND Analog signal ground
Z16
IN2+
Not used
Z14
IN2–
Z12
AGND Analog signal ground
Z10
ADO+
No connection. Not
available on standard
Z8
ADO
available on standard
unit.
Z6
Iout+
Current output high
(0
"
50 mA) Note 1
(Optionsal)
Z4
Iout–
Current output low (0
"
50 mA) Note 1
(Optionsal)
Z2
AGND Analog signal ground
Note 1: A single differential digital-to-
analog conversion channel drives all
three outputs simultaneously:
DO+/DO– = differential, SO = single-
ended, and the current output. Thus,
software controlled scaling affects all
three outputs equally.
Table 2-3A. Axis Connection Pins –
Z32 through Z2 Identical for Each Axis
