Programmable Logic Controllers
5th Edition
ISBN: 9780073373843
Author: Frank D. Petruzella
Publisher: McGraw-Hill Education
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Question
Chapter 15.4, Problem 3RQ
Program Plan Intro
Counter:
- It is similar to timer concept.
- It is used to count the changes that are produced by the state of an outside trigger signal.
- It is a Programmable Logic Controller (PLC) instruction that either counts up or down an integer value produced by the change of a bit from “0” to “1” or “false” to “true”.
- In PLC, counter contains three types, namely,
- Up counters
- Down counters
- Up/Down counters
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Students have asked these similar questions
The next problem concerns the following C code:
/copy input string x to buf */
void foo (char *x) {
char buf [8];
strcpy((char *) buf, x);
}
void callfoo() {
}
foo("ZYXWVUTSRQPONMLKJIHGFEDCBA");
Here is the corresponding machine code on a Linux/x86 machine:
0000000000400530 :
400530:
48 83 ec 18
sub
$0x18,%rsp
400534:
48 89 fe
mov
%rdi, %rsi
400537:
48 89 e7
mov
%rsp,%rdi
40053a:
e8 di fe ff ff
callq
400410
40053f:
48 83 c4 18
add
$0x18,%rsp
400543:
c3
retq
400544:
0000000000400544 :
48 83 ec 08
sub
$0x8,%rsp
400548:
bf 00 06 40 00
mov
$0x400600,%edi
40054d:
e8 de ff ff ff
callq 400530
400552:
48 83 c4 08
add
$0x8,%rsp
400556:
c3
This problem tests your understanding of the program stack. Here are some notes to
help you work the problem:
⚫ strcpy(char *dst, char *src) copies the string at address src (including
the terminating '\0' character) to address dst. It does not check the size of
the destination buffer.
• You will need to know the hex values of the following characters:
1234
3. Which line prevents compiler optimization? Circle one: 1234
Suggested solution:
Store strlen(str) in a variable before the if statement.
⚫ Remove the if statement.
Replace index 0 && index < strlen(str)) {
5 }
}
=
str [index] = val;
Character Hex value | Character Hex value Character Hex value
'A'
0x41
'J'
Ox4a
'S'
0x53
'B'
0x42
'K'
0x4b
"T"
0x54
0x43
'L'
Ox4c
'U'
0x55
0x44
'M'
0x4d
'V'
0x56
0x45
'N'
Ox4e
'W'
0x57
0x46
'0'
Ox4f
'X'
0x58
0x47
'P'
0x50
'Y'
0x59
0x48
'Q'
0x51
'Z'
Ox5a
'T'
0x49
'R'
0x52
'\0'
0x00
Now consider what happens on a Linux/x86 machine when callfoo calls foo with
the input string "ZYXWVUTSRQPONMLKJIHGFEDCBA".
A. On the left draw the state of the stack just before the execution of the instruction
at address Ox40053a; make sure to show the frames for callfoo and foo and
the exact return address, in Hex at the bottom of the callfoo frame.
Then, on the right, draw the state of the stack just after the instruction got
executed; make sure to show where the string "ZYXWVUTSRQPONMLKJIHGFEDCBA"
is placed and what part, if any, of the above return address has been overwritten.
B. Immediately after the ret instruction at address 0x400543 executes, what is
the value of the program counter register %rip?…
Chapter 15 Solutions
Programmable Logic Controllers
Ch. 15.1 - Prob. 1RQCh. 15.1 - Prob. 2RQCh. 15.1 - Prob. 3RQCh. 15.1 - Prob. 4RQCh. 15.1 - Prob. 5RQCh. 15.1 - Prob. 6RQCh. 15.1 - Prob. 7RQCh. 15.1 - Prob. 8RQCh. 15.1 - Prob. 9RQCh. 15.1 - Prob. 10RQ
Ch. 15.1 - Prob. 11RQCh. 15.1 - Compare the accessibility of program scope and...Ch. 15.1 - Prob. 13RQCh. 15.1 - What is the difference between a produced tag and...Ch. 15.1 - Prob. 15RQCh. 15.1 - State the data type used for each of the...Ch. 15.1 - Describe the make-up of a predefined structure.Ch. 15.1 - Describe the make-up of a module-defined...Ch. 15.1 - Describe the make-up of a user-defined structure.Ch. 15.1 - Prob. 20RQCh. 15.1 - Prob. 21RQCh. 15.1 - Prob. 22RQCh. 15.1 - Prob. 23RQCh. 15.2 - Prob. 1RQCh. 15.2 - Prob. 2RQCh. 15.2 - Prob. 3RQCh. 15.2 - Prob. 4RQCh. 15.2 - Prob. 5RQCh. 15.2 - Prob. 6RQCh. 15.2 - Prob. 7RQCh. 15.2 - Prob. 8RQCh. 15.2 - Prob. 9RQCh. 15.2 - Prob. 10RQCh. 15.2 - Prob. 11RQCh. 15.2 - Extend control of the original ControlLogix...Ch. 15.2 - Prob. 3PCh. 15.3 - Prob. 1RQCh. 15.3 - Prob. 2RQCh. 15.3 - Prob. 3RQCh. 15.3 - Prob. 4RQCh. 15.3 - Prob. 5RQCh. 15.3 - Prob. 6RQCh. 15.3 - Prob. 7RQCh. 15.3 - Prob. 8RQCh. 15.3 - Prob. 9RQCh. 15.3 - Prob. 10RQCh. 15.3 - Prob. 11RQCh. 15.3 - Prob. 12RQCh. 15.3 - Modify the original CLX ten-second TON timer...Ch. 15.3 - Prob. 2PCh. 15.3 - Prob. 3PCh. 15.3 - Prob. 4PCh. 15.3 - Prob. 5PCh. 15.3 - Prob. 6PCh. 15.4 - Prob. 1RQCh. 15.4 - Prob. 2RQCh. 15.4 - Prob. 3RQCh. 15.4 - Prob. 4RQCh. 15.4 - Prob. 5RQCh. 15.4 - Prob. 6RQCh. 15.4 - Prob. 7RQCh. 15.4 - Prob. 1PCh. 15.4 - Prob. 2PCh. 15.5 - Prob. 1RQCh. 15.5 - Prob. 2RQCh. 15.5 - Prob. 3RQCh. 15.5 - Prob. 4RQCh. 15.5 - Prob. 5RQCh. 15.5 - Construct a ControlLogix ladder rung with compare...Ch. 15.5 - Prob. 2PCh. 15.5 - A single pole switch is used in place of the two...Ch. 15.6 - Prob. 1RQCh. 15.6 - Name the four basic elements of an FBD.Ch. 15.6 - Prob. 3RQCh. 15.6 - Prob. 4RQCh. 15.6 - Prob. 5RQCh. 15.6 - Prob. 6RQCh. 15.6 - Prob. 7RQCh. 15.6 - Prob. 8RQCh. 15.6 - Prob. 9RQCh. 15.6 - Prob. 10RQCh. 15.6 - Prob. 11RQCh. 15.6 - How is a function block feedback loop created?Ch. 15.6 - Prob. 13RQCh. 15.6 - Prob. 14RQCh. 15.6 - Prob. 1PCh. 15.6 - Prob. 2PCh. 15.6 - Prob. 3PCh. 15.6 - Prob. 4PCh. 15.6 - Prob. 5P
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