1
Bit Logic Instructions
1.1
Overview of Bit Logic Instructions
Description
Bit logic instructions work with two digits, 1 and 0. These two digits
form the base of a number system called the binary system. The two digits 1 and
0 are called binary digits or bits. In conjunction with AND, OR, XOR and
outputs, a 1 stands for logical YES and a 0 for logical NO.
The bit logic instructions interpret signal states of 1 and 0 and combine
them according to Boolean logic. These combinations produce a result of 1 or 0
that is called the ”result of logic operation” (RLO).
There are bit
logic instructions to perform the following functions:
· AND, OR and
Exclusive OR: these instructions check the signal state and produce a result
that is either copied to the RLO bit or combined with it.
·
AND-before-OR Logic Operation and OR-before-AND Logic Operation
·
Assign and Midline Output. These instructions assign the RLO or store
it temporarily.
The following instructions
react to an RLO of 1:
· S : Set Output
·
R : Reset Output
· SR : Set_Reset Flip Flop
·
RS : Reset_Set Flip Flop
Other instructions react to a
positive or negative edge transition to perform the following functions:
· N : Negative RLO Edge Detection
· P : Positive RLO Edge Detection
· NEG : Address Negative Edge Detection
·
POS : Address Positive Edge Detection
The remaining instructions
affect the RLO directly in the following ways:
·
Insert Binary Input
·
Negate Binary Input
· SAVE : Save RLO to BR Memory
Parameter
|
Data Type
|
Memory Area
|
Description
|
<address>
|
BOOL
|
I, Q, M, T, C, D, L
|
The
address indicates the bit whose signal state will be checked.
|
Description
With the OR instruction, you
can check the signal states of two or more specified addresses at the inputs of
an OR box.
If the signal state of one of the addresses is 1, the condition is
satisfied and the instruction produces the result 1. If the signal state of all
addresses is 0, the condition is not satisfied and the instruction produces the
result 0.
If the OR instruction is the
first instruction in a string of logic operations, it saves the result of its
signal state check in the RLO bit.
Each OR instruction that is
not the first instruction in the string of logic operations combines the result
of its signal state check with the value stored in the RLO bit. These values
are combined according to the OR truth table.
Status Word
|
BR
|
CC1
|
CC0
|
OV
|
OS
|
OR
|
STA
|
RLO
|
FC
|
writes
|
-
|
-
|
-
|
-
|
-
|
X
|
X
|
X
|
1
|
Example
The following table shows the
results that arise from the OR logic operation of two operands: