User:SquidKid S/CHANS

Most info here is taken from CHANS & the CHANS parser linked there.
When parameters are used from the stack ("..."), they are used in the order in which they were PUSHed, then removed from the stack.
Scripts may defined their own functions. When these are called, parameters are placed in the highest-numbered temporary variables (which are local to each function), in numeric order; for example, with three parameters, they are placed respectively in temporary variables 0xFFD, 0xFFE, and 0xFFF.

8-bit operations

Opcode	Param	Meaning
0x00	none	return;
0x01	none	return ACC;
0x02	u8 (number of params from stack)	ACC = new ACC(...);
0x03	u16 (number of params from stack)	ACC = {...};
0x04	none	PUSH(ACC);
0x05 (?)	1 param from stack	ACC = ...;
0x06	1 param from stack	ACC = ... + ACC;
0x07	1 param from stack	ACC = ... - ACC;
0x08	1 param from stack	ACC = ... * ACC;
0x09	1 param from stack	ACC = ... / ACC;
0x0A	1 param from stack	ACC = ... % ACC;
0x0B	1 param from stack	ACC = ... & ACC;
0x0C	1 param from stack	ACC = ... \| ACC;
0x0D	1 param from stack	ACC = ... ^ ACC;
0x0E	1 param from stack	ACC = ... << ACC;
0x0F	1 param from stack	ACC = ... >> ACC;
0x10	1 param from stack	ACC = ... == ACC;
0x11	1 param from stack	ACC = ... != ACC;
0x12	1 param from stack	ACC = ... < ACC;
0x13	1 param from stack	ACC = ... > ACC;
0x14	1 param from stack	ACC = ... <= ACC;
0x15	1 param from stack	ACC = ... >= ACC;
0x17	none	ACC = !ACC;
0x18	u8 (value)	ACC = value;
0x19	u8 (value)	ACC += value;
0x1A	u8 (value)	ACC -= value;
0x1B	u8 (value)	ACC *= value;
0x1C	u8 (value)	ACC /= value;
0x1D	u8 (value)	ACC %= value;
0x1E	u8 (value)	ACC &= value;
0x1F	u8 (value)	ACC \|= value;
0x20	u8 (value)	ACC ^= value;
0x21	u8 (value)	ACC = ACC == value;
0x22	u8 (value)	ACC = ACC != value;
0x23	u8 (value)	ACC = ACC < value;
0x24	u8 (value)	ACC = ACC > value;
0x25	u8 (value)	ACC = ACC <= value;
0x26	u8 (value)	ACC = ACC >= value;
0x27	u16 (value)	ACC = value;
0x28	u32 (value)	ACC = value;
0x29 (?)	f32 (value)	ACC = value;
0x2A	f64 (value)	ACC = value;
0x2B	???	/???/
0x2C	u16 (index)	ACC = table3[index]; /* were this an actual programming language (and I get the idea that Nintendo had one that they compiled into this bytecode), string literals would probably be written in the code. */
0x2D	u8 (operation type)	/* array operation; see below. */
0x2E	???	/???/
0x2F	???	/???/
0x30	u16 (id of func in table2), u8 (number of params from stack)	ACC = ACC.func(...);
0x31	u8 (number of params from stack)	ACC = ACC(...);
0x32	u16 (id of sym in table2)	ACC = ACC.sym;
0x33	u16 (id of sym in table2), 1 param from stack	ACC.sym = ...;
0x34	???	/???/
0x35	???	/???/
0x36	???	/???/
0x37	???	/???/
0x38	???	/???/
0x39	???	/???/
0x3A	???	/???/
0x3B	???	/???/
0x3C	???	/???/
0x3D	???	/???/
0x3E	???	/???/
0x3F	???	/???/

4-bit operations

Opcode	Param	Meaning
0x4	u12 (id of locsym in table4)	ACC = locsym;
0x5	u12 (id of tempvar)	ACC = tempvar;
0x6	u12 (id of locsym in table4)	locsym = ACC;
0x7	u12 (id of tempvar)	tempvar = ACC;
0x8	u12 (id of tempvar)	/???/
0x9	???	/???/
0xA	s12 (position in bytes, 0 being the byte just after the command)	if (!ACC) goto position; /* mostly used for if-like constructions. */
0xB	???	/???/
0xC (?)	s12 (position in bytes, 0 being the byte just after the command)	if (!ACC) goto position; /* same as 0xA, though rarer. */
0xD	s12 (position in bytes, 0 being the byte just after the command)	if (ACC) goto position; /* mostly used to continue a loop. */
0xE	s12 (position in bytes, 0 being the byte just after the command)	goto position; /* mostly used for else blocks, or to jump to the condition check in a loop before starting it. */
0xF	u12 (id of tempvar)	/???/