The As10k1's assembly syntax was originally intended to be similar to MC68K assembly. It has since evolved and now has a unique syntax.
Assembly lines generally have four fields separated by spaces or tabs:
| Name_Field | Opcode_field | Operand_Field | Comment_Field |
|---|---|---|---|
| [symbol] | [mnemonic] | [operands] | [text] |
With this assembler, each line can have a maximum of 256 characters and each symbol can be a maximum of 11 characters. Symbols ARE case sensitive, opcodes ARE NOT.
Symbols
A symbols is a words which placed at the beginning of a line (it must start at column 1) and is used by assembly directive. Symbols may be used to reference a register, an assembly-time equate, to reference a position in the program (the skip instruction), or just as a label to indicate to a reader where they are in a program (e.g. "start"). The use of a symbol is covered in greater detail in the sections describing assembly directives.
The first character in a symbol must be an alpha character* (a-z,A-Z). The remaining characters may be alphanumeric (a-z,A-Z,0-9) or an underscore (_). Symbols cannot exceed a length of 32 characters.
*An exception to this rule occurs when symbols are used for the skip command, in which case the symbol must start with a period.
Opcode
All instructions require 4 operands, they have the format
opcode R,A,X,Y
Here is a summary of the 16 opcodes. [1]
| Opcode Number | Opcode Mnemonic | Instruction | comment |
|---|---|---|---|
| 0x0 | MACS | R = A + (X * Y >> 31) | saturation |
| 0x1 | MACS1 | R = A + (-X * Y >> 31) | saturation |
| 0x2 | MACW | R = A + (X * Y >> 31) | wraparound |
| 0x3 | MACW1 | R = A + (-X * Y >> 31) | wraparound |
| 0x4 | MACINTS | R = A + X * Y | saturation |
| 0x5 | MACINTW | R = A + X * Y | wraparound (31-bit) |
| 0x6 | ACC3 | R = A + X + Y | saturation |
| 0x7 | MACMV | R = A, acc += X * Y | 67 bit accum, you can grab MS 32 bits of LS 32 bits |
| 0x8 | ANDXOR | R = (A & X) ^ Y | |
| 0x9 | TSTNEG | R = (A >= Y) ? X : ~X | |
| 0xa | LIMIT | R = (A >= Y) ? X : Y | |
| 0xb | LIMIT1 | R = (A < Y) ? X : Y | |
| 0xc | LOG | ... | |
| 0xd | EXP | ... | |
| 0xe | INTERP | R = A + (X * (Y - A) >> 31) | ; saturation |
| 0xf | SKIP | R,CCR,CC_TEST,COUNT |
Operands
Operands can be specified as either a symbol or a value. hex values are prefixed by $, octal by @, and binary by %.
e.g.:
123 decimal value
$123 hex value
@123 octal value
%01101 binary value
The operands for emu10k1 instructions are always addresses of registers, there are no instruction which take immediate values.
Some directives have there own special operand forms
Comments
A semicolon ";" indicates to the assembler that everything afterwards is a comment.
Anything after a completed instruction (i.e. one that has four operands) will also be ignored. However, to be on the safe side, I recommend aways using a ";" to make sure that the assembler knows to ignore what follows.
Example
Here's an example of an instruction:
foo macs one,two,three,four ;comment
"foo" is a symbol (in this case it does nothing), "macs" is our instruction, and "one,two,three,four" is our operand, ";comment" is ignored.