; Basic assembly to machine language converter
;
; bits 0-3 Address of next instruction
; bits 4-7 Data bits
; bits 8-9 Light register instruction bits
; bits 10-12 Accumulator instruction bits
; bit 13 Conditional Jump bit
; J C C C L L D D D D A A A A
;

The simple assembly language provides a convenient interface with which to
design programs for the small computer specified by Lab 1.  It translates
mnemonics to machine instructions that can be loaded into the program memory
unit.  Each line of the assembly source file translates into one machine
instruction.  Each instruction can specify the values of each of the following
parameters:  the address of the next instruction (using 'goto'), the data
bits, the light register command, the accumulator command, and the value of
the conditional jump bit.  Note that the order in which commands are specifed
on an instruction line does not matter.  Comments begin with a semi-colon and
extend to the end of the line.  

Specifying the next address:  A 'goto' command on a line causes the program to
jump to the specified instruction.  The instructions are numbered starting at
0, so the command " goto.0 " jumps to the first instruction in the program.
Since the program memory can hold only 16 instructions, the legal values for
the addresses range from 0 to 15.  If an instruction line doesn't have goto
command, the default next address is the next instruction.

Specifying the data value:  Data values are specified in hexadecimal.

Specifying the light register command:  The 'lr' identifier specifies the
light register, and the possible commands are listed below.

Specifying the accumulator register command: The 'ac' identifier specifies the
accumulator register, and the possible commands are listed below.

Specifying the jump bit:  Simply include the 'jmp' identifier on a line to set
the conditional jump bit.

For the data value, light, and accumulator register commands, if nothing is
specified on an instruction line, the previous command is used.  The defaults
are indicated below also.


; Syntax of "assembly" language. Comments begin with ; 
; Up to sixteen instruction lines can exist in a program.
;
; Light register instructions:
;
; default: Reload							hold
; Load from instruction data			loadins
; Load from accumulator output			loadacc
; Inverse										invert
;
; Accumulator Register instructions:
;
; default: Hold the same value			hold
; Load from instruction register		loadins
; Load from light register				loadli
; Invert the bits							invert
; Add one										add1
; Subtract one								sub1
; Shift left									shiftl
; Shift right								shiftr
;
; example program that does about nothing

data.0x2 lr.loadacc ac.loadins jmp
data.0x3 goto.0