B-32
5 Buffer Memory (BFM)
5.4 Details of Buffer Memories
FX
3U
/FX
3UC
Series PLC User's Manual - Analog Control Edition
FX3UC-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 < lower limit error set value":
The lower limit error bit will be turned on.
• If "channel data > upper limit error set value":
The upper limit error bit will be turned on.
→ For a detailed description of upper/lower limit error status data resetting, refer to Subsection
5.4.18.
1. Assignment of each bit of BFM #26
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.
• Even if an error is detected, channel data (BFM #10 to #13) will continuously be 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.
Only when the upper/lower error 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.
: 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 #26 →
D
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