In comparison, analog devices represent physical quantities that can have an infinite number of values. A fault condition that caused a shutdownģ2 ANALOG I/O MODULES Discrete devices are inputs and outputs that have only two states: on and off.A shift register can be used to simulate the movement, or track the flow, of parts and information Common applications for shift registers include the following: Tracking of parts through an assembly line Controlling of machine or process operations Inventory control System diagnosticsģ1 Data in the shift register could represent the following: The bit shift register shifts bits serially (from bit to bit) through an array in an orderly fashion.
The convert from BCD (FRD) instruction is used to convert binary-coded decimal (BCD) values to integer values.ģ0 BIT SHIFT REGISTERS A bit shift register is a register that allows the shifting of bits through a single register or group of registers. Moving data Comparison of magnitude of data( greater than, equal to, less than) Arithmetic operation (Addition & subtraction) Conversion between binary coded decimal, binary, octal.Ģ6 DATA COMPARISON EQUAL TO NOT EQUAL TO GREATER THANĢ7 DATA COMPARISON LESS THAN LESS THAN OR EQUAL LIMIT TESTĢ8 ARITHMETIC OPERATION ADDITION SUBTRACTION MULTIPLICATION DIVISIONĢ9 TO BINARY CODED DECIMAL FROM BINARY CODED DECIMALĬONVERSION TO BINARY CODED DECIMAL FROM BINARY CODED DECIMAL The convert to BCD (TOD) instruction is used to convert 16-bit integers into binary-coded decimal (BCD) values. Each time the down-count event occurs, the accumulated value is decremented. A retentive timer (RTO) accumulates time whenever the device receives power, and it maintains the current time should power be removed from the device.Ģ0 DOWN-COUNTER The down-counter instruction will count down or decrement by 1 each time the counted event occurs. The off-delay timer (TOF) operation will keep the output energized for a time period after the rung containing the timer has gone false. On-delay timer (TON) Off-delay timer (TOF) Retentive timer on (RTO)ġ2 ON-DELAY TIMER (TON) An on-delay timer is used when you want to program a time delay before an instruction becomes true.ġ4 OFF-DELAY TIMER (TOF) and RETENTIVE TIMER ON (RTO)
The output instruction is like a relay coilĤ matrix limitation diagram for a typical PLC.Ī maximum of seven parallel lines and 10 series contacts per rung is possible.Ĩ Programming a PLC : In order to create or change a program, the following items are needed: PLC Programming Device Programming Software Connector Cableĩ You can use a personal computer as a programming deviceġ0 Instructions Timers Counters Master control Jump control Data handlingġ1 TIMERS In general, there are three different PLC timer types: A Load Bar (normally closed contact) symbol An OUT (coil) symbol Out :The Out instruction is sometimes also called an Output Energize instruction. Load: The load (LD) instruction is a normally open contact A Load (contact) symbol Load Bar: The Load Bar instruction is a normally closed contact. Structured Text (ST) -a high-level, text-based language such as BASIC, C, or PASCAL specifically developed for industrial control applications.Instruction List (IL) -a low-level, text-based language that uses mnemonic instructions.Sequential Function Chart (SFC) -a graphical depiction of interconnecting steps, actions, and transitions.Function Block Diagram (FBD) -a graphical depiction of process flow using simple and complex interconnecting blocks.
Ladder Diagram (LD) -a graphical depiction of a process with rungs of logic, similar to the relay ladder logic schemes that were replaced by PLCs.The standard IEC (International Electro technical Commission) was established to standardize the multiple languages associated with PLC programming by defining the following five standard languages: