Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 134)

Publication AG-UM008C-EN-P - February 2005
3-66 Configuring MicroLogix 1100/1200/1500 Controllers
Records Stored (RST)
Records Stored (RST) specifies how many data sets are in the queue.
RST is decremented when a record is read from a communications
device. To address this word in ladder logic, use the format:
DLS0:Q.RST, where Q is the queue number.
DLS information can be used in the following types of instructions:
Retrieving (Reading) Records
Data is retrieved from a data logging queue by sending a logical read
command that addresses the Data Log retrieval file. The oldest record
is retrieved first and then, deleted. The record is deleted as soon as it
is queued for transmission. If there is a power failure before the
transmission is complete, the record is lost.
TIP
If a queue is full and another record is saved, the
oldest record is over-written. Queue behavior is the
same as a FIFO stack—first in, first out. If a queue is
full and an additional record is saved, the ‘first’
record is deleted.
Instruction Type Operand
Relay (Bit) Destination Output Bit
Compare Source A
Source B
Low Limit (LIM instruction)
Test (LIM instruction)
High Limit (LIM instruction)
Source (MEQ instruction)
Mask (MEQ instruction)
Compare (MEQ instruction)
Math Source A
Source B
Input (SCP instruction)
Logical Source A
Source B
Move Source