help

Curses interface
PLC-EMU's interface consists of 5 monitoring windows, and a Ladder editor.
You can switch between windows with the left/right arrows.
Up/down arrows scroll windows.

F4 starts/stops PLC task.
F7 loads a program and initialization file
F8 saves current PLC state as initial state, and current LD task to a file
that can later be used as a program file.
F9 displays this help.
F10 quits.
Tab gets quickly to editor window.

Inputs/Outputs window
Here you can see the current state of I/O.
When an I/O is green, it is set to 1.(although you can also read the value "1")
When it is red, it means it has been forced.

F1 forces current input/output to 1.
F2 forces to 0.
F3 unforces.
F5 edits comments for single I/Os.

Memory window
Here you can see the value of internal memory registers.
Green means that the counter is receiving a pulse.
Red means that a counter has been disabled, and only its pulse is used 
as a boolean variable.

F1 sends a positive pulse to the counter
F2 stops pulse
F5 edits comments, value and up/down counting
F6 enables/disables counting

Timers window
Timers state is displayed here, in the form:
T[index] X [scale] 	[value]/[preset].
Green means the timer is counting.
Red means the timer has reached its preset value, and its output is positive.
F1 starts timer
F2 stops it
F5 edits comments, value, preset, scale i.e. how many cycles are needed to 
increase value by 1, and whether it is in TON/TOFF mode.

Blinkers window

Here the current state of blinkers is displayed, in the form
S[index] X[scale].
Green means that blinkers'output is 1.
F5 you can edit comments and scale value

Program editor

When the PLC is in STOP mode, you can edit your PLC task in a plain text editor.
Tabs, Copy/paste, select etc. are not supported-sorry.
Ctrl-X saves and returns to monitoring windows. 
If you have an error in your ladder diagram, it will not be executed and an 
error message will be displayed. 
In RUN mode, F5 toggles the language interpreter from Ladder to Instruction List and vice versa.

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.