1-10
Section 1 Specifications
1-3-6 System FB instance memory area
The user FB memory area is a real memory area dedicated to the system FBs such as timers, counters, and differential
instructions that are used internally in the PLC.
G
Key points:
1) At PLC startup, predefined initialization is performed. (the old values are retained or reset to 0s (zeros).
Example) The current values for the counters and additional timers and the old value for the edge detect instruction
counter are retained, while the current values for the timers (excluding additional) are reset to 0s (zeros).
2) Eight words/timer, four words/counter, and two words/edge detect instruction counter are used.
3) The size of the system FB instance memory area can be changed taking those of other areas into account.
For the details of memory size change, see “3-3-2 CPU memory size definition.”
4) By default, the numbers of timers, additional timers, counters, and edge detect instruction counters have been preset
per main unit. If necessary, you can change these numbers.
To set the timer, additional timer, counter, edge detect, and other system FB areas, the following conditions must be
met.
(No. of timers) × 8 words + (No. of counters) × 4 words + (No. of edge detect counters) × 2 words + Others
<= Preset size of system FB instance memory area
5) You can select whether or not to clear the memory for saved attributes in this area when transferring the project.
Timer
Additional
timer
Counter
Edge detect Others
Main unit with 14/24 points
256 points
0 point
256 points
1024 points
512 words
Main unit with 32/40/60 points 512 points
0 point
512 points
2048 points
1024 words
