Buffer Memory; Buffer Memory List - Mitsubishi Electric MELSEC FX Series User Manual

FX -4LC User's Manual
3U
8.

Buffer Memory

Each setting and alarm in the 4LC is written from or read to the PLC main unit through buffer memories.
To read or write to the 4LC buffer memory, use FROM/TO instructions or specify buffer memory values
directly.
Each buffer memory consists of 16 bits. Use the FROM/TO instructions (or direct specification of buffer
memory) in the 16-bit format.
Caution
• If a value is written by mistake to a buffer memory used only for read, the written value is ignored.
And 250ms later, the buffer memory is overwritten with a correct value.
• If a value outside the allowable set range is written to a buffer memory used both for read and write, the set
value range error (b1) of the flag (BFM#0) turns ON. The buffer memory number in which an error has
been generated is stored in a set value range error address (BFM#252). And the buffer memory in which
the set value range error has occurred is controlled with the upper limit or the lower limit of the allowable
set range.
8.1

Buffer Memory List

The table below provides a brief description and reference information for the 4LC buffer memory.
The "Remarks" column in the buffer memory list indicates the following.
R/W : Read or Write
R : Read only
: Data can be backed-up using the set value backup command (BFM#254).
: Handling numbers containing decimal places.
The set value should be the actual value multiplied by ten.
The set value should be the actual value multiplied by "100" for the sensor correction value setting
buffer memories (BFM#68, BFM#108, BFM#148 and BFM#188), and multiplied by "1000" for the
cascade gain buffer memories (BFM#246 and BFM#247).
: Handling integers or numbers containing decimal places according to the input range
(setting of BFM#208, #214, #220 and #226).
When handling numbers containing decimal places, multiply the set value by ten.
BFM No.
CH1 CH2 CH3 CH4
#0
#1 #2 #3
#5 #6 #7
#9 #10 #11
#13 #14 #15
#17 #18 #19
#21 #22 #23
#25 #26 #27
#29
#30
#31
→ For details of FROM/TO instructions (or direct specification of buffer memory),
Name
Flag
#4 Event
#8 Measured value (PV)
Control output value (MV)
PID control
monitor
#12
Heating/cooling Heating control output value
PID control (MV) monitor
PID control Not used
#16
Heating/cooling Cooling control output value
PID control (MV) monitor
#20 Control output flag
#24 Heater current measured value
#28 External input value
Control start/stop changeover
FX Series model code
Not used
refer to the Programming Manual.
→ For details on the buffer memory, refer to Section 8.2.
Description/set range
Refer to Subsection 8.2.1.
Refer to Subsection 8.2.2.
±5% of input range
Output limiter upper limit to
output limiter lower limit
-50 to heating output limiter
upper limit (-5.0% to )
-50 to cooling output limiter
upper limit (-5.0% to )
Refer to Subsection 8.2.6.
0 to 1050 (0.0 to 105.0A)
-32768 to +32767
0 : Stops control
1 : Starts control
K2090
8 Buffer Memory
8.1 Buffer Memory List
Initial
Remarks
value
- R
- R
- R
- R
-
- R
- R
- R
0 R/W
0 R/W
2090 R
- - -
1
2
3
4
5
6
7
- -
8
- -
-
-
9
-
- -
-
- -
10
- -
- -
- -
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