AutomationDirect DL205 - Page 379

DL205 User Manual, 4th Edition, Rev. D
5-155
Chapter 5: Standard RLL Instructions
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A
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D
In the following example, when X1 is on, the constant value (K6) is loaded into the accumulator
using the Load instruction. This value specifies the length of the table and is placed in the
first stack location after the Load Address instruction is executed. The octal address 1400
(V1400) is the starting location for the source table and is loaded into the accumulator.
Remember, V1400 is used as the pointer location, and is not actually part of the table data
source. The destination location (V1500) is specified in the Table to Destination instruction.
The table pointer (V1400 in this case) will be increased by “1” after each execution of the TTD
instruction.
It is important to understand how the table
locations are numbered. If you examine the
example table, you’ll notice that the first data
location, V1401, will be used when the pointer is
equal to 0, and again when the pointer is equal to
6. Why? Because the pointer is only equal to 0
before the very first execution. From then on, it
increments from 1 to 6, and then resets to 1.
Also, our example uses a normal input contact (X1) to
control the execution. Since the CPU scan is extremely
fast, and the pointer increments automatically, the table
would cycle through the locations very quickly. If this is a
problem, you have an option of using SP56 in conjunction
with a one-shot (PD) and a latch (C1 for example) to
allow the table to cycle through all locations one time and
then stop. The logic shown here is not required, it’s just
an optional method.
X1
LD
K6
LDA
0 1400
TTD
V1500
Load the constant value 6
(HEX) into the lower 16 bits
of the accumulator
Convert octal 1400 to HEX
300 and load the value into
the accumulator. This is the
table pointer location
Copy the specified value from
the table to the specified
destination (V1500)
Handheld Programmer Keystrokes
STR
$
SHFT
ANDST
L
3
D
SHFT
MLR
T
MLR
T
3
D
PREV
1
B
ENT
6
G
0
A
0
A
ENT
SHFT
ANDST
L
3
D
1
B
4
E
0
A
ENT
0
A
1
B
5
F
0
A
ENT
DirectSOFT
DirectSOFT Display (optional latch example using SP56)
LD
K6
C1
C0
SP56
X1
C0
PD
C1
SET
Since Special Relays are
reset at the end of the scan,
this latch must follow the TTD
instruction in the program.
Load the constant value 6
(HEX) into the lower 16 bits
of the accumulator
C1
RST
V
1401
0500
V
1402 9999
V
1403
3074
V
1404
8989
V
1405 1010
V
1406
2046
V
1407
XXXX
V1500
XXXX
1
2
3
4
5
0 6
V1400
000
Table
Table Pointer
Destination
.
.
0