317
Analog Input Terminals
Section 5-7
ing figure. (There is no effect during current input, even if the power supply is
shared.)
When portion A in the above diagram is disconnected, the sneak circuit indi-
cated by
→
will be formed. As a result, despite the disconnection, a voltage
equivalent to 1/2 to 1/3 of the output of the connected input device is gener-
ated at the disconnected input device. (The same is true if portion B is discon-
nected.) When this kind of voltage is generated, the burnout detection
function may fail to activate.
For voltage input, either do not have the power supply shared by the input
devices, or use an isolator for each input.
AD Conversion Data
When the AD conversion data becomes negative, it is expressed as 2
’
s com-
plement. The NEG instruction can be used to obtain the absolute value from
this 2
’
s complement.
Conversion Time
AD conversion data is updated every 1 ms for each point.
V+
I+
–
V+
I+
–
A
B
Power
supply
Input
device
Analog Input Terminal
Voltage
generated
Internal
circuits
Input
device
Bit
First word
Input 0 AD conversion data
First word +1
Input 1 AD conversion data
Input 2 AD conversion data
Input 3 AD conversion data
First word +2
First word + 3
3
0
2
1
4
6
5
7
8
10
9
11
12
14 13
15
