Mitsubishi Electronics MELSEC-F Manuel D’Utilisation
B-34
5 Buffer Memory (BFM)
5.4 Buffer Memory Details
FX
3G
/FX
3U
/FX
3UC
PLC User's Manual - Analog Control Edition
FX
3U
-4AD/FX
3UC
-4AD (4-channel Analog Input)
5.4.9
BFM #26: Upper/lower limit error status
Initial value: H0000
Numeric data type: Hexadecimal (H)
If channel data (BFM #10 to #13) is out of the range set by the lower limit error data (BFM #71 to #74) and the
upper limit error data (BFM #81 to #84), the following operation will be performed:
• If "channel data
upper limit error data (BFM #81 to #84), the following operation will be performed:
• If "channel data
< lower limit error set value":
The lower limit error bit will turn on.
• If "channel data
> upper limit error set value":
The upper limit error bit will turn on.
→ For a detailed description of upper/lower limit error status data resetting,
refer to Subsection 5.4.18.
1. BFM #26 bit assignment
The upper and lower limit error values of each channel are assigned as shown in the following table:
2. Cautions regarding use of upper/lower limit error status data
• To use the upper/lower limit error status data, be sure to turn on the upper/lower limit detection function (b1
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 b0 or b1 of BFM #99 to reset the upper/lower limit error status.
- Write "H0000" in BFM #26 as the upper/lower limit error status data.
- Turn on b0 or b1 of BFM #99 to reset the upper/lower limit error status.
- Write "H0000" in BFM #26 as the upper/lower limit error status data.
• Even if an error is detected, channel data (BFM #10 to #13) will be continuously updated.
3. Upper/lower limit error status data automatic transfer function (b5 of BFM #22)
If the upper/lower limit error status data automatic transfer-to data register is specified in BFM #126, the data
in BFM #26 can be transferred to the specified data register.
When the upper/lower error is detected, data will be automatically transferred from the 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.
in BFM #26 can be transferred to the specified data register.
When the upper/lower error is detected, data will be automatically transferred from the 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.
: Represents a numeric value.
Bit No.
Channel number
Description
b0
ch1
Lower limit error value
b1
Upper limit error value
b2
ch2
Lower limit error value
b3
Upper limit error value
b4
ch3
Lower limit error value
b5
Upper limit error value
b6
ch4
Lower limit error value
b7
Upper limit error value
b8 to b15
Not used.
Convenient function
setting
Automatic data transfer function
ON = Valid
Transfer-from buffer memory
Transfer-to data register specification
(BFM #126: K )
BFM #22 b1:ON
BFM #22 b5:ON
BFM #22 b5:ON
BFM #26
→
D