help

The default UI for version 2.0 onwards is command line based.

This is just a std prompt where the PLC's internal state in YAML format is monitored, while PLC commands can be issued.

Supported commands:

START

start plc loop

STOP

stop plc loop

HELP

display help message

QUIT

close the UI

EDIT <sequence><index><key: value>

Edit a configuration for any input, output or other sequence block. The key: value pair can be any of the parameters in the configuration of the specific block.

FORCE<sequence><index><value>

This will force a value on a sequence block for debugging purposes.

UNFORCE<sequence><index>

Reverts the FORCE command.

LOAD<filename>

Load configuration in yml file

SAVE<filename>

Save current configuration, if filename given save as yml file otherwise default config.yml

Program Structure

The program file consists of two sections: init section, and PLC task section,
separated by the keywords "LD" or "IL".

Initialization
In the init section, you can write the initialization state of the plc, in the 
format <VARIABLE>	<INDEX>		<VALUE> separated by tabs.

Supported variables are:

Text variables 
Up to 16 character comments.

I:	comment associated with input[index]
Q:	comment associated with output[index]
M:	comment associated with memory register[index]
T:	comment associated with timer register[index]
S:	comment associated with timer register[index]

Integer variables
Non negative numbers.

MEMORY:	initial value of register[index]	
TIME:	number of time cycles timer[index] takes to increase its value by 1.
PRESET:	preset value of timer[index]
BLINK:	number of time cycles blinker[index] takes to change state.

Unique value variables: 
Boolean variables which, if they are not set, are presumed to work with their 
default values. So it only makes sense to initialize them in their non-default 
states. 

COUNT:	setting this to DOWN means register[index] works as an downcounter.
COUNTER:setting this to OFF means register[index] is just a boolean variable.
DELAY:	setting this to ON means timer[index] is a T-ON counter. default is T-OFF

LD task
Everything after the keyword "LD", is supposed to be in Ladder diagram format.
The version of LD PLC-EMU supports, consists of the following operators and 
operands, in a diagram of maximum 1024 characters wide, and random lines long.

Operators
These are the accepted symbols that can exist along with the operands.

'-' propagates a boolean state horizontally, from left to right. 
Thus, it works as a logical "AND". 

'+' changes line and can join states of up to 3 different lines, 
like a logical "OR" .

'|' propagates a state vertically, both ways between aligned "+" nodes.

'!' negates the state of the following operand like a logical "NOT"

'(' open contact. this propagates a state directly to an output. the following operand must be an output.

')' negate contact. this propagates the opposite of a state to an output. the following operand must be an output.

'[' set coil. if this is ON, thestate of an output is set. the following operand must be an output.

']' reset coil. if this is ON, thestate of an output is reset. the following operand must be an output.

';' end of line. anything after that is considered "comments".

Blank characters interrupt lines, so be careful.

Input operands 
These can appear anywhere in a line before a '(', followed by a valid 
non negative index. Valid values of indexes are dependant on the operand and
the configuration. This means, that if you have 16 timers and 64 inputs, you
can write t14 and i62, but not t45 or i567.
In every cycle, their values are polled and propagated to the diagram. 
Accepted symbols (case sensitive) are:

'i' digital input state

'q' digital output state

'r' rising edge of digital input

'f' falling edge of digital input

'm' pulse state of counter

't' output of timer

'b' output of blinker

'c' true, if serial input byte equals following index

Output operands
These symbols must follow operator '(' and be followed by a valid index.
Each output operand should appear only once.

'Q' digital output

'M' pulse of counter

'T' timer 

'W' write following number to serial output.

Example of a valid Program file:

I	1	My button
I	3	My other button
Q	1	My led
Q	2	My other led
M	1	My bool variable
M	4	My up-counter
T	1 	My on-timer
S	3	My blinker
MEMORY	4	654	
COUNT	4	DOWN	
COUNTER	1	OFF	
TIME	1	500	
PRESET	1	20	
DELAY	1	ON
BLINK	3	40	

LD
  
 r1---------!m1----------(Q0    ;rising input 1 and not pulse of counter 1 contacts 
                                ;output 1
 t1---+
 b3---+---i2-----+             	;timer 1 or blinker 3 or falling edge of input
      |		 |		;3 and input 2
      |          |              ;sets pulse of counter 4. 
 f3---+          +--------[M4
 
 c255------------+--------(T1   ;command 255 starts timer 1 and sets output 2
                 +--------[Q1
 b1-----------+-----------]T1   ;blinker 1 stops timer 1, 
	      |	                ;resets pulse of counter 4 and output 1
	      |                 ;and writes byte 99 to serial output
              +-----------]Q1       
              +-----------]M4
              +-----------(W99


IL task

Alternatively, you can use the keyword "IL" (or F5 in the editor window) 
to define a IEC61131-3 compatible Instruction List program. 
Currently, subroutines are not implemented.

Just like standard Instruction List, all instructions store their result to an
internal Accumulator register, while "ST" stores the Accumulator's value to its operand.

A line of an IL program, shall follow the format:

[label:]<operator>[<modifier>[%<operand><byte>[/<bit>]]|<label>][;comment]

Supported Operators are:

	) 	close parenthesis (pop instruction from stack)
	S 	set output
	R 	reset output
	    
	AND 
	OR
	XOR

	LD 	load 
	ST 	store

	ADD	
	SUB	subtract
	MUL	multiply
	DIV	divide
	GT	>
	GE	>=
	NE	<>
	EQ	==
	LE	<=
	LT	<
	JMP	jump to label

Modifier symbols recognized are:
	(	open parenthesis (push instruction to stack)
	!	negate
	?	conditional
	
Operands are the same as in LD, with the difference that it is assumed that 
they are Words (unsigned Integers), unless noted otherwise with the symbol '/'.

As defined in the IEC standard, each instruction supports its own set of data types
and modifiers, according to the following scheme:

Instruction 	Modifiers 	Data Types
	) 	N/A		N/A
	S 	N/A		BOOL
	R 	N/A		BOOL
	    
	AND 	!,(		BOOL/WORD
	OR	!,(		BOOL/WORD
	XOR	!,(		BOOL/WORD

	LD 	!		BOOL/WORD
	ST 	!		BOOL/WORD

	ADD	(		BOOL/WORD
	SUB	(		BOOL/WORD
	MUL	(		BOOL/WORD
	DIV	(		BOOL/WORD
	GT	(		BOOL/WORD
	GE	(		BOOL/WORD
	NE	(		BOOL/WORD
	EQ	(		BOOL/WORD
	LE	(		BOOL/WORD
	LT	(		BOOL/WORD
	JMP	?		CHARACTER STRING



You can write a text file with the initialization and task program externally
and then load it into PLC-EMU, or use the curses interface to edit and save it.