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more cleanup

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~d6 2024-08-02 11:35:19 -04:00
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uxntal.1
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@ -8,18 +8,19 @@ Uxntal is an 8-bit instruction set for programming the Varvara virtual machine.
It uses the lower 5-bits to specify an opcode, and the upper 3-bits to specify
optional modes.
ROMs consist of a 16-bit address space of bytes. Any byte can be interpreted as either data or an instruction. A 2-byte instruction pointer determines the address of the next instruction to decode and run.
ROMs consist of a 16-bit address space of bytes. Any byte can be interpreted as either data or an instruction. A 2-byte program counter (\fIpc\fP) determines the address of the next instruction to decode and run.
Instructions manipulate data using two stacks: a working stack (\fBwst\fP) and a return stack (\fBrst\fP). Each stack consists of 256 bytes, and in the case of overflow or underflow the stack pointer will wrap (the stacks are circular).
There are also 256 bytes of device memory, which are used to interact with the virtual machine and its devices.
.SH INSTRUCTION LAYOUT
0x01 -
0x02 \\
0x04 +- \fIopcode\fP
0x08 /
0x10 -
0x01 ----
0x02 \\
0x04 +- \fIopcode\fP
0x08 /
0x10 ----
0x20 ---- 2: \fIshort\fP mode
0x40 ---- r: \fIreturn\fP mode
0x80 ---- k: \fIkeep\fP mode
@ -131,7 +132,7 @@ Store data at a zero-page address (\fB0x0000 - 0x00ff\fP).
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 \fBpc\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
@ -139,7 +140,7 @@ Note that unlike \fBLDZk\fP and \fBLDAk\fP the \fBLDRk\fP instruction is not ver
Store data at a relative address (\fBpc + x\fP).
Note that unlike \fBSTZk\fP and \fBSTAk\fP the \fBSTRk\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 \fBpc\fP value).
Note that unlike \fBSTZk\fP and \fBSTAk\fP the \fBSTRk\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 LDA
( abs* -- x )