DL205 User Manual, 4th Edition, Rev. D
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Chapter 5: Standard RLL Instructions
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A
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D
Add to Top (ATT)
The Add To Top instruction pushes a value onto a V-memory
table from a V-memory location. When the value is added to
the table, all other values are pushed down 1 location.
The instruction will be executed once per scan provided the
input remains on. The function parameters are loaded into the first level of the accumulator
stack and the accumulator by 2 additional instructions. Listed below are the steps necessary to
program the Add To Top function.
Step 1: Load the length of the table (number of V-memory locations) into the first level of the
accumulator stack. This parameter must be a HEX value, 0 to FF.
Step 2: Load the starting V-memory location for the table into the accumulator. (Remember, the
starting location of the table is used as the table length counter.) This parameter must be a
HEX value.
Step 3: Insert the ATT instruction that specifies the source V-memory location (Vaaa). This is where
the value will be moved from.
Helpful hint: For parameters that require HEX values when referencing memory locations, the
LDA instruction can be used to convert an octal address to the HEX equivalent and load the
value into the accumulator.
Helpful hint: The instruction will be executed every scan if the input logic is on. If you do not
want the instruction to execute for more than one scan, a one shot (PD) should be used in the
input logic.
Helpful hint: The table counter value should be set to indicate the starting point for the
operation. Also, it must be set to a value that is within the length of the table. For example, if
the table is 6 words long, then the allowable range of values that could be in the table counter
should be between 1 and 6. If the value is outside of this range or zero, the data will not be
moved into the table. Also, a one shot (PD) should be used so the value will only be set in one
scan and will not affect the instruction operation.
NOTE: Status flags (SPs) are only valid until:
— another instruction that uses the same flag is executed, or
— the end of the scan
The pointer for this instruction can be set to start anywhere in the table. It is not set automatically. You
have to load a value into the pointer somewhere in your program.
ATT
V aaa
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250-1
260
Discrete Bit Flags Description
SP56 On when the table counter equals 0.
Operand Data Type DL260 Range
aaa
V-memory V All (See page 3-56)
DS Used
HPP Used
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