Parker Hannifin S.p.A S.B.C. Division
SLVDN User’s Manual
Page 124 of 181
FUNCTIONAL DESCRIPTION
The pico-PLC program is scanned every 6.144 milliseconds. With this sampling, the input
is first read, the two timers (Pr92 Pr93 b99.0 and b99.1) are updated, the user program is
scanned and the output is updated. For this reason reading the input and setting the output can
vary by 6.144 ms with respect to the physical event. If the microprocessor is overloaded with
work (the operating mode is active, there are frequent serial requests and the PLC program is
long), it may take more than 6.144 milliseconds to scan the entire PLC program.
All the instructions of the pico-PLC with the exception of the arithmetic instructions are
single bit instructions. The available stack has a depth of only one bit.
The LD (LDN) instruction loads the bit defined as the operant on the stack with all the
other logical instructions work on the stack itself. The arithmetic instructions are executed
only if the stack bit is set to 1.
The truth table for the logical operations is given below for the convenience of the user.
The respective negative operations ANDN and ORN follow the same logic except that the
negated value of the bit specified will be used.
12 bits from b90.4 to b90.15 are reserved on the PLC and can be stored. 14 additional bits
from b91.2 to b91.15 are available on the PLC but cannot be stored. They are always set to 0
when the converter is powered on.
10 word parameters are also reserved. These are from Pr80 to Pr88. They can be stored and
used as 5 double word parameters just as the 13 parameters from Pr151 to Pr163. The pico-
PLC includes 9 constants for arithmetic operations. These are from Pr71 to Pr79 and can be
the constants most used by normal applications.
When the arithmetic operations (ADD, SUB, MUL, DIV) are used, the operators are
assumed to be words and are signed. If a double word operation is required, set b94.0 = 1
before the operation itself. After the operation the PLC will automatically set this bit to 0. The
parameters Pr58...Pr69 and Pr110...Pr149 are treated as double words so that in an operation
such as [ADD 71 72 64] the result –1 will be written in the double word Pr64:65 without
having to set b94.0=1 before the operation. If Pr80=-1 and Pr81=0 the operation [ADD 80 72
64] will give the result Pr64:65=-1, while the same operation executed with b94.0=1 will
assume Pr81 as the high word of the double word Pr80:81 and the result will be
Pr64:65=65535. In the first case, operators other than Pr58...Pr69, Pr110...Pr149 are treated as
words, while in the second case they are treated as double words.
OR logical operation
bit A
bit B
result
0 0 0
0 1 1
1 0 1
1 1 1
AND logical operation
bit A
bit B
result
0 0 0
0 1 0
1 0 0
1 1 1
