digital-to-analog conversion to output an analog voltage or current. The output
level is maintained until updated by the CR1000.
8.2.7 PLC Control Modules — Overview
Related Topics:
• PLC Control — Overview (p. 74)
• PLC Control — Details (p. 244)
• PLC Control Modules — Overview (p. 368)
• PLC Control Modules — Lists (p. 648)
• PLC Control — Instructions (p. 562)
• Switched Voltage Output — Specifications
• Switched Voltage Output — Overview
• Switched Voltage Output — Details
(p. 103)
Controlling power to an external device is a common function of the CR1000.
On-board control terminals and peripheral devices are available for binary (on /
off) or analog (variable) control. A switched, 12 Vdc terminal (SW12V) is also
available. See the section Switched Unregulated (Nominal 12 Volt)
(p. 105).
8.2.7.1 Terminals Configured for Control
C terminals can be configured as output ports so set low (0 Vdc) or high (5 Vdc)
using the PortSet() or WriteIO() instructions. Ports C4, C5, and C7 can be
configured for pulse width modulation with maximum periods of 36.4 s, 9.1 s, and
2.27 s, respectively. A terminal configured for digital I/O is normally used to
operate an external relay-driver circuit because the port itself has limited drive
capacity. Drive capacity is determined by the 5 Vdc supply and a 330 Ω output
resistance. It is expressed as:
V
o
= 4.9 V – (330 Ω) • I
o
Where V
o
is the drive limit, and I
o
is the current required by the external device.
Figure Control Port Current Sourcing
(p. 369) plots the relationship.
368
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