Assembler Syntax
Note: where expressions are required below, the current assembler accepts Decimal, Octal and Hex constants and their negations. i.e. 1, 0FH, -0FH, 17B. Note that hex constants must begin with a decimal digit. For similar reasons, the output bytes are supplied with a leading 0 digit.
Goal Symbol: SingleInstruction => I | LC | LR | LB | LH | LW | LBD | RRR | QR | RD | XO | XRO
I =>
I—Instruction
I—Instruction => I-format instructions from the Dragon Instruction Set summary plus the J1, J2, J3, and J5 instructions which the assembly coder should consider to be I-format and less the LCm instructions (use LC).
LC => LC
m: an expression
this is actually a macro instruction: it will choose the appropriate instruction LCm, LIB, LIDB, or LIQB depending on the value of the expression
ConstantRegisterIndex => an expression in [0..12) | -1 | -2 | 80000000H
-1, -2, and FIRST[INT] are translated to the appropriate constant register index.
LR =>
LR—Instruction
n:
AuxOrLocalRegisterIndex
LR—Instruction => LRn | SRn
AuxOrLocalRegisterIndex => an expression
IN [0..16)
LB =>
LB—Instruction
Byte
LB—Instruction => LB-format instructions from the Dragon Instruction Set summary.
Byte => an expression IN [-128..256)
LH =>
LH—Instruction Halfword
LH—Instruction => LH-format instructions from the Dragon Instruction Set summary.
Halfword => an expression
IN [-32768..65535)
LW =>
LW—Instruction Word
LW—Instruction => LW-format instructions from the Dragon Instruction Set summary.
LBD =>
LBD—Instruction
comparand:
Byte ,
displacement:
Byte
LBD—Instruction => LBD-format instructions from the Dragon Instruction Set summary.
RRR =>
RRR—Instruction
c:
DestinationReg ,
a:
SourceReg ,
b:
SourceReg
RRR—Instruction => RRR-format instructions from the Dragon Instruction Set summary.
DestinationReg => GeneralReg | Push
SourceReg => GeneralReg | PopTop | PopUnder
GeneralReg =>
AUX
AuxOrLocalRegisterIndex |
LOCAL
AuxOrLocalRegisterIndex |
CONSTANT
ConstantRegisterIndex |
Top | Under
QR =>
QR—Instruction
ca:
CASpec ,
b:
SourceReg
QR—Instruction => QR-format instructions from the Dragon Instruction Set summary.
CASpec => TopATop | PushATop | PushA0 | PushA1
RD =>
RD—Instruction
s:
ShortSourceReg ,
b:
SourceReg ,
displacement:
Byte
RD—Instruction => RD-format instructions from the Dragon Instruction Set summary.
ShortSourceReg => Constant0 | Constant1 | Top | PopTop
XO =>
XO—Instruction
n:
AuxOrLocalRegisterIndex ,
offset:
Byte
XO—Instruction => LRIn | SRIn
XRO =>
XRO—Instruction
a:
SourceReg ,
b:
SourceReg ,
offset:
Byte
XRO—Instruction => XRO-format instructions from the Dragon Instruction Set summary.