all instructions supported

This commit is contained in:
~d6 2024-08-02 13:26:17 -04:00
parent d1dd621ba0
commit 8b5854c43b
1 changed files with 58 additions and 1 deletions

View File

@ -90,15 +90,23 @@ Thus for regular instructions writing a "generic" effect (leaving sigils off val
.SS EQU .SS EQU
( x y -- x==y^ ) ( x y -- x==y^ )
Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
.SS NEQ .SS NEQ
( x y -- x!=y^ ) ( x y -- x!=y^ )
Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
.SS GTH .SS GTH
( x y -- x>y^ ) ( x y -- x>y^ )
Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
.SS LTH .SS LTH
( x y -- x<y^ ) ( x y -- x<y^ )
Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
.SS JMP .SS JMP
( x -- ; pc <- x ) ( x -- ; pc <- x )
@ -134,7 +142,6 @@ Load data from a relative address (\fBpc + x\fP).
Note that unlike \fBLDZk\fP and \fBLDAk\fP the \fBLDRk\fP instruction is not very useful, since a relative address is usually only meaningful when run from a particular address (i.e. for a particular \fIpc\fP value). Note that unlike \fBLDZk\fP and \fBLDAk\fP the \fBLDRk\fP instruction is not very useful, since a relative address is usually only meaningful when run from a particular address (i.e. for a particular \fIpc\fP value).
.SS STR .SS STR
( x rel^ -- ) ( x rel^ -- )
@ -166,6 +173,56 @@ Write data to a device port (\fB0x00 - 0xff\fP).
Writing to some ports may have an effect on the underlying VM; in other cases it will simply write values to device memory. See Varvara device documentation for more details. Writing to some ports may have an effect on the underlying VM; in other cases it will simply write values to device memory. See Varvara device documentation for more details.
.SS ADD
( x y -- x+y )
Overflow will be truncated, so \fB#ff #03 ADD\fP will evaluate to \fB0x02\fP.
.SS SUB
( x y -- x-y )
Underflow will be truncated, so \fB#01 #03 SUB\fP will evaluate to \fB0xfe\fP.
.SS MUL
( x y -- xy )
Overflow will be truncated, so \fB#11 #11 MUL\fP will evaluate to \fB0x21\fP.
.SS DIV
( x y -- x/y )
\fBDIV\fP implements \fIEuclidean division\fP, which is also known as \fIinteger division\fP. It returns whole numbers, so \fB#08 #09 DIV\fP evaluates to \fB0x00\fP.
Division by zero will return zero (instead of signaling an error).
Unlike \fBADD\fP, \fBSUB\fP, and \fBMUL\fP, \fBDIV\fP does not behave correctly for numbers which should be treated as signed. For example, the signed byte representation of \fB-2\fP is \fB0xfe\fP, but \fB#06 #fe DIV\fP evaluates to \fB0x00\fP (\fB6 / 254 = 0\fP). For signed values the correct result should instead be \fB0xfd\fP (\fB6 / -2 = -3\fP).
There is no \fIremainder\fP instruction, but the phrase \fBDIVk MUL SUB\fP can be used to compute the remainder.
.SS AND
( x y -- x&y )
.SS ORA
( x y -- x|y )
.SS EOR
( x y -- x^y )
.SS SFT
( x rl^ -- (x>>l)<<r )
Given a byte \fIrl\fP consisting of a low nibble (\fIl\fP) and a high nibble (\fIh\fP), this instruction shifts \fIx\fP left by \fIl\fP and then right by \fIr\fP.
Right shifts are unsigned (they introduce zero bits); there are no signed shifts.
Since the largest values (\fIshort\fP) are 16-bit, one nibble (\fB0x0 - 0xf\fP) is sufficient to express all useful left or right shifts.
Right: \fB#ff #03 SFT\fP evaluates to \fB0x1f\fP.
Left: \fB#ff #20 SFT\fP evaluates to \fB0xfc\fP.
Both: \fB#ff #23 SFT\fP evaluates to \fB0x7c\fP.
.SH SPECIAL INSTRUCTIONS .SH SPECIAL INSTRUCTIONS
These instructions do not accept all mode flags (some do not accept any). These instructions do not accept all mode flags (some do not accept any).