Mitsubishi FX3U-4AD - BFM #200 to #6999: Data History

B-50
5 Buffer Memory (BFM)
5.4 Buffer Memory Details
FX 3G /FX 3U /FX 3UC PLC User's Manual - Analog Control Edition
FX3U-4AD/FX3UC-4AD (4-channel Analog Input)
5.4.29 BFM #200 to #6999: Data history
Initial value: K0
Numeric data type: Decimal (K)
Use this function to sample the A/D conversion data of each channel and to write the sampled data to the
buffer memories.
The 4AD can sample up to 1,700 points of A/D conversion data of each channel at the sampling cycle
specified in BFM #198, and can store the sampled data as history data in the buffer memories as shown in
the following table. Buffer memories are assigned to the 4 channels as shown in the following table, and data
is stored in the buffer memories in the order of the smallest BFM number to the largest BFM number.
Use BFM #199 to stop or reset the data history.
1. Caution regarding data history reading
If a large amount of history data is collectively read out to the PLC main unit using the FROM instruction, the
watchdog timer error may occur in the PLC main unit. Therefore, when programming, separate the history
data and then read it out using the FROM instruction. Set WDT (watchdog timer refresh) instruction between
the separated data.
Number of data
samples
BFM number
ch1 ch2 ch3 ch4
1st #200 #1900 #3600 #5300
2nd #201 #1901 #3601 #4301
3rd #202 #1902 #3602 #4302
… … … … …
1,700th #1899 #3599 #5299 #6999