Automation Direct DL405 User Manual page 225

Before you begin writing the control program, it is important to take a few minutes to
understand how the module processes and represents the analog signals.
Channel The F4–04DA module allows you to update the channels in any order. Your control
program determines which channel gets updated on any given scan by turning off a
Scanning
Sequence bit that is associated with each channel. With a DL440 or DL450 CPU, you can use
immediate instructions to update all four channels in the same scan (we will show
you how to do this later).
Scan
Read inputs
Execute Application Program
Calculate the data
Write data
Write to outputs
F4–04DA 4-Channel Analog Output
Scan N
Scan N+1
Scan N+2
Scan N+3
Scan N+4
12–9
Channel 1
Channel 2
Channel 3
Channel 4
Channel 1