PLC Session 2 Flashcards
What slot does the power supply of a PLC occupy?
It does not take a slot number. Only power supply, input, output modules get a slot number.
What are the two kinds of scans the CPU can perform
Asynchronous
Synchronous
What kinds of inputs can you have?
Discreet
Analog
What are the four modes of PLC operation?
- Run Mode
- Program Mode
- Test Mode
- Online\Offline mode
What are two types of Tags we use?
- Base Tags
2. Alias Tags
What are the 6 data types we use in programming a PLC?
- Bool (True or False)
- Sint (-128 to +127)
- Int (Word) (-32768 to 32767)
- Dint (Double Word) (-2,147,483,648 to +2,147,483,647)
- Timer (
- Counter
What is Bool?
A true of false value in memory
What is a Sint?
Memory value Sint (-128 to +127)
What is a Int?
A memory value of a word (-32768 to 32767)
What is a Dint?
A memory value (Double Word) (-2,147,483,648 to +2,147,483,647)
What 5 bits are in Timer?
.EN BOOL The enable bit indicates the TIMER instruction is enabled.
.TT BOOL The timing bit indicates that a timing operation is in process
.DN BOOL The done bit behaves like the associated hard-wired timer
.PRE DINT The preset value specifies the value in msec which the programmer sets
.ACC DINT The accumulated value specifies the number of milliseconds that have elapsed since the instruction was enabled (on delay)/
disabled (off-delay).
What does the .EN BOOL bit in a timer do?
The .EN enable bit indicates the TIMER instruction is enabled.
What does the .TT BOOL bit in a timer do?
The .TT timing bit indicates that a timing operation is in process
What does the .DN Bool bit in a timer do?
The .DN done bit behaves like the associated hard-wired timer
What does the .PRE bit in a timer do?
The .PRE preset value specifies the value in msec which the programmer sets
What does the .ACC bit in a timer do?
The .ACC accumulated value specifies the number of milliseconds that have elapsed since the instruction was enabled (on delay)/
disabled (off-delay).
What does the Latch bit do?
It sets the Latch data bit. Which stays until it’s unlatched.
What does a One-Shot bit do?
A one-shot is an instruction that will only allow logic past it for 1 scan provided the previous instruction(s) is true
What does the .CU bit in counter do?
The. CU count up enable bit indicates the CTU instruction is enabled
What does the .DN bit in a counter do?
The done bit indicates that Accumulated value count has exceeded the Preset value to count to.
What does the .OV bit in a counter do?
The .OV overflow bit indicates the counter exceeded the upper limit of 2,147,483,647. The counter then rolls over to -2,147,483,648 and begins counting up aga
What does the .UN bit in a counter do?
The .UN underflow bit indicates that the counter exceeded the lower limit of -2,147,483,647. The counter then rolls over to 2,147,483,647 and begins counting down again.
What does the .PRE bit in counter do?
The .PRE preset value specifies the value which the accumulated value must reach before the instruction sets the .DN
What does the .ACC bit in a counter do?
The .ACC accumulated value specifies the number of transitions the instruction has counted.
What will shutdown all outputs in a system?
The Master Control Relay (MCR)
What is used in AC output of PLC modules to suppress noise and surges
MOV Metal Oxide Varistor
What is test mode on a PLC?
PLC reads inputs, but does not activate outputs.
Does Sinking and Sourcing apply to DC and AC circuits?
No, it only applies to DC circuits.
Describe a Sinking input on a PLC?
DC Circuit. Battery negative is connected to “Common” on PLC Input board. Positive from battery goes through switch (or other device) to input on PLC board.