Cricket Bytecode Generation

Cricket Bytecode

The following table lists Cricket bytecode. Each bytecode is listed with its opcode, mnemonic, whether it will create value on the Cricket VM stack, and the number of operands it will take, and a description of the operation.

Opcode	Mnemonic	Create Stack value?	Number of operands	Description
0	code-end	no	0	terminates code
1	byte	yes	followed by 1 byte	convert follow up byte immediate value to 16-bit unsigned number and pushed onto stack (value 0-255).
2	number	yes	followed by 2 bytes	convert follow up 2 bytes immediate value to 16-bit number and pushed onto stack
3	list	no	0	"start of list"; opens a code block, followed by number of bytes of list (excluding list opcode and the list length byte, but including eol)
4	eol	no	0	"end of list"; closes a code block
5	eolr	yes	0	"end of list reporter"; closes a code block that will create a stack value
6	lthing	yes	1	"local thing"; push to stack the function arguments, followed by index of call arguments in reverse order: 0 is arg_n (last argument), 1 is arg_n-1, etc. Example: for foo(a, b, c, d), d will be refered as lthing 0, c as lthing 1, b as lthing 2, a as lthing 3.
7	stop	no	0	void return from callee function to caller
8	output	no	1	return value from callee to caller
9	repeat	no	2	repeats code block for specific number of times, first operand is loop count, second operand is loop body, represented as a list.
10	if	no	2	if input expression is true, executes true branch, first operand is test conditional expression, second operand is true branch code block
11	ifelse	no	3	if input expression is true, executes true branch, else executes false branch, first operand is test conditional, second operand is true branch code block, third operand is false branch code block
12	beep	no	0	causes Cricket to beep
13	note	no	2	makes Cricket play note of specified pitch and duration, first operand is pitch, second operand is duration
14	waituntil	no	1	repeatedly executes body block until condition block evaluates to true, first operand is condition expression, second operand is body code block
15	loop	no	1	unconditional loop to executes body block, operand is body block
16	wait	no	1	waits for specified time period, operand is time is 1/10 second
17	timer	yes	0	push to stack value of system timer
18	resett	no	0	resets system timer to zero
19	send	no	1	sends specified value out IR port, with 0.1 sec trailing delay, operand is the send value
20	ir	yes	0	push to stack the value of most recently received IR byte
21	newir?	yes	0	push to stack whether IR value has been received since last call to "ir"
22	random	yes	0	push to stack pseudorandom 16 bit value
23	+	yes	2	push to stack sum of two inputs
24	-	yes	2	push to stack difference of two imputs
25	*	yes	2	push to stack product of two inputs
26	/	yes	2	push to stack division of two inputs
27	%	yes	2	push to stack remainder of division of two inputs
28	=	yes	2	push to stack boolean equality of two inputs
29	>	yes	2	push to stack boolean "greater than" of two inputs
30	<	yes	2	push to stack boolean "less than" of two inputs
31	and	yes	2	push to stack bitwise AND of two inputs
32	or	yes	2	push to stack bitwise OR of two inputs
33	xor	yes	2	push to stack bitwise XOR of two inputs
34	not	yes	1	push to stack (0x0001 and (input XOR 0x0001)). In other words, does a NOT on the low bit and push to stack just that low bit. If you need bitwise not, XOR with 0xffff.
35	setglobal	no	2	sets numbered global to value
36	global	yes	1	push to stack value of numbered global
37	aset	no	3	sets numbered array with numbered element to value
38	aget	yes	2	push to stack value of numbered element of numbered array
39	record	no	1	records 8-bit value into data buffer
40	recall	yes	0	push to stack 8-bit value stored in data buffer
41	resetdp	no	0	resets data buffer pointer to zero
42	setdp	no	1	sets data buffer pointer to specified value
43	erase	no	1	erases data point
44	when	no	2	sets up daemon with condition block and action block
45	whenoff	no	0	terminates "when" daemon
46	a,	no	0	selects motor A for control
47	b,	no	0	selects motor B for control
48	ab,	no	0	selects motors A and B
49	on	no	0	turns on selected motor(s)
50	onfor	no	1	turns on selected motor(s) for specified period of time
51	off	no	0	turns off selectec motor(s)
52	thisway	no	0	sets selected motor(s) direction to green LED
53	thatway	no	0	sets selected motor(s) direction to red LED
54	rd	no	0	reverses direction of selected motor(s)
55	sensora	yes	0	push to stack value of sensor A
56	sensorb	yes	0	push to stack value of sensor B
57	switcha	yes	0	push to stack boolean value of sensor A
58	switchb	yes	0	push to stack boolean value of sensor B
59	setpower	no	1	sets power level of selected motor(s), first operand is the value
60	brake	no	0	sets selected motor(s) for active braking
61	bsend	no	1	sends value out Bus Port
62	bsr	yes	1	sends value out Bus Port and push reply value to stack, operand is the value
63	c,	no	0	selects bus motor C for control
64	d,	no	0	selects bus motor D for control
65	cd,	no	0	selects bus motors C and D for control
66	abcd,	no	0	selects all motors for control
67	fastsend	no	1	sends specified value out IR port without trailing delay, first operand is the value
68	stop!	no	0	terminates execution completely, system exit
69	eb	yes	1	"examine byte"; push to stack the value of Cricket memory at specified address, operand is the address
70	db	no	2	"deposit byte"; store byte into Cricket memory, first operand is address, second operand is value
71	low-byte	yes	1	push to stack low byte of operand
72	high-byte	yes	1	push to stack high byte of operand

 

Function Call Bytecode (or The Lack Of)

Cricket does not have dedicated function call bytecode, the generated bytecode sequence for function call is:

take the 16-bit function address, bit OR the address with 0x8000, and the result is two bytes for function call.
For examle, the main function memory address is at: 0x00, call main will be:
0x0000 | 0x8000 (expand to 16bit)-> 0x80 0x00, or -128, 0.
In general, if the highest bit of a bytecode is set, it indicates a function call, and use the above rule to determine the function address.

Chirp Binary File Format

Chirp has a simple binary format and is defined as following:

Acknowledgements

• The information on Cricket bytecode is based on the Cricket bytecode specification by Prof. Fred Martin. The original technical information on Cricket controller is at handyboard.com/cricket.