Standard
RLL Instructions
5–8
Standard RLL Instructions
Boolean Instructions
The DL05 Micro PLCs can usually complete an operation cycle in a matter of
milliseconds. However, in some applications you may not be able to wait a few
milliseconds until the next I/O update occurs. The DL05 PLCs offer Immediate input
and outputs which are special boolean instructions that allow reading directly from
inputs and writing directly to outputs during the program execution portion of the
CPU cycle. You may recall that this is normally done during the input or output
update portion of the CPU cycle. The immediate instructions take longer to execute
because the program execution is interrupted while the CPU reads or writes the I/O
point. This function is not normally done until the read inputs or the write outputs
portion of the CPU cycle.
NOTE: Even though the immediate input instruction reads the most current status
from the input point, it only uses the results to solve that one instruction. It does not
use the new status to update the image register. Therefore, any regular instructions
that follow will still use the image register values. Any immediate instructions that
follow will access the I/O again to update the status. The immediate output
instruction will write the status to the I/O and update the image register.
X0
OFF
X1
OFF
CPU Scan
Read Inputs
Diagnostics
Input Image Register
The CPU reads the inputs from the local
base and stores the status in an input
image register.
X0 Y0
X0X1X2...X11
OFFOFFON...OFF
Solve the Application Program
Read Inputs from Specialty I/O
Write Outputs
Write Outputs to Specialty I/O
X0
ON
X1
OFF
Immediate instruction does not use the
input image register, but instead reads
the status from the module immediately.
I/O Point X0 Changes
I
Immediate Boolean
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