33A3BEPM-W4 At power-up in RUN mode, or when the processor is switched from PROG to
RUN, the user program enables a block transfer read. Then it initiates a block
transfer write to configure the module and send data values.
Thereafter, the program continuously performs read block transfers and write
block transfers.
Two’s Complement Binary Two’s complement binary is used when performing mathematical calculations
internal to the processor. To complement a number means to change it to a
negative number. For example, the following binary number is equal to decimal
22.
0 101102 = 2210
First, the two’s complement method places an extra bit (sign bit) in the left–most
position, and lets this bit determine whether the number is positive or negative.
The number is positive if the sign bit is 0 and negative if the sign bit is 1. Using
the complement method:
0 10110 = 22
To get the negative using the two’s complement method, you must invert each bit
from right to left after the first ”1” is detected.
In the above example:
0 10110 = +22
Its two’s complement would be:
1 01010 = –22
Note that in the above representation for +22, starting from the right, the first
digit is a 0 so it is not inverted; the second digit is a 1 so it is not inverted. All
digits after this one are inverted.
If a negative number is given in two’s complement, its complement (a positive
number) is found in the same way:
1 10010 = –14 0 01110 = +14
All bits from right to left are inverted after the first ”1” is detected.
TIP You must create the data file for the block transfers before you enter
the block transfer instructions
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84 Module Programming
The two’s complement of 0 is not found, since no first ”1” is ever encountered in
the number. The two’s complement of 0 then is still 0.
Analog Data Format The data returned from the analog-to-digital converter in the module is 12-bit
resolute. This value is left-justified into a 16-bit field, reserving the most
significant bit for a sign bit.
Current and Voltage Mode Values
Current (mA) 4…20 mA Mode 0…20 mA Mode Voltage (V) ± 10V Mode 0…10V Mode
Input Output
-10.50 8000 8000
0.00 0000 -10.00 8620 8618
1.00 0618 -9.00 9250 9248
2.00 0C30 -8.00 9E80 9E78
3.00 1248 -7.00 AAB0 AAA8
4.00 0000 1860 -6.00 B6E0 B6D8
5.00 0787 1E78 -5.00 C310 C310
6.00 0F0F 2490 -4.00 CF40 CF40
7.00 1696 2AA8 -3.00 DB70 DB70
8.00 1E1E 30C0 -2.00 E7A0 E7A0
9.00 25A5 36D8 -1.00 F3D0 F3D0
10.00 2D2D 3CF0 0.00 0000 0000 0000
11.00 34B4 4310 1.00 0C30 0C30 0C30
12.00 3C3C 4928 2.00 1860 1860 1860
13.00 43C3 4F40 3.00 2490 2490 2490
14.00 4B4B 5558 4.00 30C0 30C0 30C0
15.00 52D2 5B70 5.00 3CF0 3CF0 3CF0
14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
11 10 09 08 07 06 05 04 03 02 01 00
S
S
14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
10 09 08 07 06 05 04 03 02 01 00
S
S
14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
11 10 09 08 07 06 05 04 03 02 01 00
0*
A/D unipolar data
A/D bipolar data
D/A data
Output
Input
Analog value
Analog value
Analog value
* = Always positive xxxxx
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Module Programming 85
Scaling Example
To scale your data to a different range:
• SLC™ 500 – use the scaling instruction.
• PLC-5 – determine a constant (slope) by dividing the desired range by the
actual range. Multiply the result by your data, and add or subtract any
offset.
Example using Compute Instructions
This rung scales FLEX I/O analog data to a different range. In this example, we
want the 4…20 mA input data to represent 0…537.7°C (32…1000°F) in the
PLC-5. N13:0 = 30,840 (7878 in hex). Two compute instructions are needed
because of the way the destination value is rounded if we use an integer location
16.00 5A5A 6188 6.00 4920 4928 4928
17.00 61E1 67A0 7.00 5550 5558 5558
18.00 6969 6DB8 8.00 6180 6188 6188
19.00 70F0 73D0 9.00 6DB0 6DB8 6DB8
20.00 7878 79E8 10.00 79E0 79E8 79E8
21.00 7FFF 7FF8 10.50 7FF0 7FF8 7FF8
Current and Voltage Mode Values
Current (mA) 4…20 mA Mode 0…20 mA Mode Voltage (V) ± 10V Mode 0…10V Mode
Input Output
EXAMPLE A 4…20 mA input places data at N13:0 (see figure PLC-5
Family Sample Program Structure for a 1794-OE4 Module on
page 82), with a range of 0…30,840. (30,840 = 7878 hex – see
table Current and Voltage Mode Values on page 84).
You want the 4…20 mA (0…30,840) to be 0…537.7°C
(32…1000°F) in the PLC-5. Use the following formula:
= {[(1000 - 32)/30,840] X N13:0} + 32
F8:0
Scaled Data (degrees) @ N30:0 = {[(Desired Range)/Actual Range] X Analog Input Data} + O ffset
= F8:0 + 32
Scaled Data (degrees) @ N30:0 (See ladder logic below) = F8:0 + 32
Publication 1794-UM062B-EN-P - March 2020
86 Module Programming
instead of a floating point in the first compute instruction. The second compute
instruction has a final destination of an integer location.
CPT
1
B3:0 DN
ER
02
05
03
Enable
Done
Error
Power-up Bit1
B4:8
15
1 Power-up bit included in Series B modules only.
1
2
TIP You must create the data file for the block transfers before
you enter the block transfer instructions.
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80 Module Programming
PLC-3 Family Sample Program Structure for a 1794-OE4 Module
Program Action
At power-up in RUN mode, or when the processor is switched from PROG to
RUN, the user program enables a block transfer read. Then it initiates a block
transfer write to configure the module and send data values.
Thereafter, the program continuously performs read block transfers and write
block transfers.
PLC-3 Family Sample Program Structure for a 1794-IE4XOE2 Module
EN
BTR
BLOCK TRANSFER READ
RACK:
GROUP:
SLOT:
DATA FILE:
7
1
0
B7:0
LENGTH:
CONTROL:
1
B6:0
05
B6:0
15
DN
ER
Block Transfer
Read Done Bit
B6:0
Block Transfer
Write Done Bit
12
15
13
Enable
Done
Error
EN
BTR
BLOCK TRANSFER WRITE
RACK:
GROUP:
SLOT:
DATA FILE:
7
1
0
B8:0
LENGTH:
CONTROL:
14
B6:0 DN
ER
02
05
03
Enable
Done
Error
1
2
TIP You must create the data file for the block transfers before you enter
the block transfer instructions
EN
BTR
BLOCK TRANSFER READ
RACK:
GROUP:
SLOT:
DATA FILE:
7
2
0
B10:0
LENGTH:
CONTROL:
5
B9:0
05
B9:0
15
DN
ER
Block Transfer
Read Done Bit
B9:0
Block Transfer
Write Done Bit EN
BTR
BLOCK TRANSFER WRITE
RACK:
GROUP:
SLOT:
DATA FILE:
7
2
0
B11:0
LENGTH:
CONTROL:
8
B9:0 DN
ER
1
2
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Module Programming 81
Program Action
At power-up in RUN mode, or when the processor is switched from PROG to
RUN, the user program enables a block transfer read. Then it initiates a block
transfer write to configure the module and send data values.
Thereafter, the program continuously performs read block transfers and write
block transfers.
PLC-5 Programming
The PLC-5® program is very similar to the PLC-3 program with the following
exceptions:
• block transfer enable bits are used instead of done bits as the conditions on
each rung.
• separate block transfer control files are used for the block transfer
instructions.
PLC-5 Family Sample Program Structure for a 1794-IE8 Module
Program Action
At power-up in RUN mode, or when the processor is switched from PROG to
RUN, the user program enables a block transfer read. Then it initiates a block
transfer write to configure the modul |
