Mitsubishi Electronics MELSEC-F Manuel D’Utilisation
B-35
5 Buffer Memory (BFM)
5.4 Buffer Memory Details
A
Comm
on I
te
te
ms
B
FX
3U
-4AD
FX
3UC
-4
A
D
C
FX
3U
-4A
D
D
-A
D
P
D
FX
3G
-2A
D
D
-BD
E
FX
3U
-4DA
F
FX
3U
-4D
A
A
-AD
P
P
G
FX
3G
-1D
A
A
-BD
H
FX
3U
-3
A-
ADP
I
FX
3U
-4
A
D
-P
T
-
A
D
P
J
FX
3U
-4A
D
D
-P
TW
-
A
A
D
P
FX
3G
/FX
3U
/FX
3UC
PLC User's Manual - Analog Control Edition
FX
3U
-4AD/FX
3UC
-4AD (4-channel Analog Input)
5.4.10 BFM #27: Abrupt change detection status
Initial value: H0000
Numeric data type: Hexadecimal (H)
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)
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 turn on.
• If "(previous value) - (new value)
> (abrupt change detection value)":
The "-" direction bit will turn on.
→ For a detailed description of abrupt change detection status data resetting,
refer to Subsection 5.4.18.
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:
the following table:
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 to reset the abrupt change detection error status.
- Write "H0000" in BFM #27 as the abrupt change detection status data.
- Turn on b2 of BFM #99 to 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 be continuously 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.
When abrupt change is detected, data will be automatically transferred from the 4AD to the PLC. For this
reason, the PLC does not need any program for reading the data, and the scan time of the PLC can be
shortened.
data in BFM #27 can be transferred to the specified data register.
When abrupt change is detected, data will be automatically transferred from the 4AD to the PLC. For this
reason, the PLC does not need any program for reading the data, and the scan time of the PLC can be
shortened.
: Represents a numeric value.
Bit No.
Channel number
Description
b0
ch1
"-" direction for abrupt change detection
b1
"+" direction for abrupt change detection
b2
ch2
"-" direction for abrupt change detection
b3
"+" direction for abrupt change detection
b4
ch3
"-" direction for abrupt change detection
b5
"+" direction for abrupt change detection
b6
ch4
"-" direction for abrupt change detection
b7
"+" direction for abrupt change detection
b8 to b15
Not used.
Convenient function
setting
Automatic data transfer function
ON = Valid
Transfer-from memory
Transfer-to data register specification
(BFM #127: K )
BFM #22 b2:ON
BFM #22 b6:ON
BFM #22 b6:ON
BFM #27
→
D