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FX2N-8AD Analog input block Buffer Memory (BFM) 8
8-41
8.2.25 BFM #200 to BFM #3399: Data history
The A/D conversion of each channel is sampled, and written to BFM #200 to BFM #3399.
The table below shows the assignment of channel No. and BFM No. Data is stored in turn from
the smallest BFM No.
Up to 400 values can be stored for each channel. When the number of values exceeds "400",
the existing data is overwritten with new data from the smallest BFM No.
Data history sampling is valid only in channels for which the number of times of averaging
(BFM #2 to #9) is set to "1".
• If much data history is read at a time to the PLC main unit by one FROM instruction, a watch
dog timer error occurs in the PLC main unit.
In such a case, divide the required data history using many FROM instructions, and insert
the WDT instruction (watch dog timer refresh instruction) after each FROM instruction.
Table 8.16: Assignment of channel No. and BFM No.
Channel No.
BFM No.
1st value 2nd value 3rd value • • • • • 400th value
CH1 #200 #201 #202 • • • • • #599
CH2 #600 #601 #602 • • • • • #999
CH3 #1000 #1001 #1002 • • • • • #1399
CH4 #1400 #1401 #1402 • • • • • #1799
CH5 #1800 #1801 #1802 • • • • • #2199
CH6 #2200 #2201 #2202 • • • • • #2599
CH7 #2600 #2601 #2602 • • • • • #2999
CH8 #3000 #3001 #3002 • • • • • #3399