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CONFIGURATION
FUNCTION BLOCKS
4 - 2
I-E96-213A
®
2. Specify the number of blocks for both types. In this exam-
ple, 205 Square Root blocks, 205 PID blocks, and 2 additional
Segment Control blocks are configured.
3. Assign priorities to segments of these function blocks. Give
the segment of blocks controlling the most critical functions
the highest priority. The execution rates are listed in Table
4. Calculate the amount of NVM the configuration uses:
a. Multiply 205 PID blocks by 36 bytes per block = 7,380
bytes of NVM.
b. Multiply 205 Square Root blocks by 12 bytes per block
= 2,460 bytes of NVM.
c.
Multiply 2 Segment Control blocks by 60 bytes per
block = 120 bytes of NVM.
d. Add products:
7,380
2,460
+
120
9,960 bytes of NVM
There are 29,496 bytes available at the beginning. There are
19,536 bytes of NVM remaining.
5. Calculate the amount of RAM the configuration uses:
a. PID blocks use 116 bytes. Therefore, multiply 205 PID
blocks by 116 = 23,780 bytes RAM.
b. Square Root blocks use 44 bytes. Therefore, multiply
205 Square Root blocks by 44 = 9,020 bytes RAM.
c.
Segment Control blocks use 256 bytes. Therefore, mul-
tiply 2 Segment Control blocks by 256 = 512 bytes RAM.
Table 4-1. Function Block Execution Rates
Control Type
Rate of
Execution
PID
Block
Square Root
Block
Critical Control
20 times/second
5
5
Normal Priority Control Loops
4 times/second
100
100
Low Priority Control Loops
1 time/2 seconds
100
100