5.4.10 Bfm #27: Abrupt Change Detection Status - Mitsubishi MELSEC-F FX3U Series User Manual

FX /FX Series PLC User's Manual - Analog Control Edition
3U 3UC
FX -4AD (4-channel Analog Input)
3UC

5.4.10 BFM #27: Abrupt change detection status

When channel data (BFM #10 to #13) is updated, if the difference between the previous value and the new
value is larger than the set abrupt change detection value (value set in BFM #91 to #94), the following
operation will be performed:
• If "(new value) - (previous value) > (abrupt change detection value)":
The "+" direction bit will be turned on.
• If "(previous value) - (new value) > (abrupt change detection value)":
The "-" direction bit will be turned on.
→ For a detailed description of abrupt change detection status data resetting, refer to Subsection
1. Assignment of each bit of BFM #27
For the abrupt change detection function of each channel, the "+" and "-" directions are assigned as shown in
the following table:
Bit No. Channel number
b0
b1
b2
b3
b4
b5
b6
b7
b8 to b15
2. Caution regarding use of abrupt change detection status data
• To use the abrupt change status data, be sure to turn on the abrupt change detection function (b2 of BFM
#22).
• Perform one of the following operations to turn off the previously turned on bit:
- Turn the power off and on.
- Turn on b2 of BFM #99 reset the abrupt change detection error status.
- Write "H0000" in BFM #27 as the abrupt change detection status data.
• Even if abrupt change is detected, channel data (BFM #10 to #13) will continuously be updated.
3. Abrupt change detection status data automatic transfer function (b6 of BFM #22)
If the abrupt change detection status data automatic transfer-to data register is specified in BFM #127, the
data in BFM #27 can be transferred to the specified data register.
Only when abrupt change is detected, data will be automatically transferred from 4AD to the PLC. For this
reason, the PLC does not need the program for reading data, and the scanning time of the PLC can be
shortened.
Convenient function
setting
ON = Valid
BFM #22 b2:ON
BFM #22 b6:ON
"-" direction for abrupt change detection
ch1
"+" direction for abrupt change detection
"-" direction for abrupt change detection
ch2
"+" direction for abrupt change detection
"-" direction for abrupt change detection
ch3
"+" direction for abrupt change detection
"-" direction for abrupt change detection
ch4
"+" direction for abrupt change detection
Not used.
Transfer-from memory
BFM #27
Numeric data type: Hexadecimal (H)
Description
Automatic data transfer function
Transfer-to data register specification
→
5 Buffer Memory (BFM)
5.4 Details of Buffer Memories
Initial value: H0000
5.4.18.
: Represents a numeric value.
(BFM #127: K )
D
B-33
A
B
C
D
E
F
G