59 lines
3.2 KiB
Markdown
59 lines
3.2 KiB
Markdown
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# Varvara
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[Varvara](https://wiki.xxiivv.com/site/varvara.html) is a personal computer, using the [uxn](./uxn.md) instruction set, programmed in [tal](./tal.md)
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UXN presents 16 I/O ports via the `DEI` and `DEO` instructions.
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Each port consists of 16 words of memory, and has its own I/O memory mapping behavior.
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Note that while other memory read and write instructions can interface with port memory, only `DEI` and `DEO` will trigger port effects.
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The Varvara computer presents the following canonical port mappings -
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- `0x0`, System device
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- `0x1`, Console device (text output)
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- `0x2`, Screen device (bitmap output)
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- `0x3`, Audio device (`audio0`)
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- `0x4`, Audio device (`audio1`)
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- `0x5`, Audio device (`audio2`)
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- `0x6`, Audio device (`audio3`)
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- `0x7`, Unused
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- `0x8`, D-pad controller
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- `0x9`, Mouse
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- `0xA`, File (`file0`)
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- `0xB`, File (`file1`)
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- `0xC`, Datetime
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- `0xD`, Unused
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- `0xE`, Unused
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- `0xF`, Unused
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```
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|00 @System &vector $2 &wst $1 &rst $1 &eaddr $2 &ecode $1 &pad $1 &r $2 &g $2 &b $2 &debug $1 &halt $1
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|10 @Console &vector $2 &read $1 &pad $5 &write $1 &error $1
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|20 @Screen &vector $2 &width $2 &height $2 &auto $1 &pad $1 &x $2 &y $2 &addr $2 &pixel $1 &sprite $1
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|30 @Audio0 &vector $2 &position $2 &output $1 &pad $3 &adsr $2 &length $2 &addr $2 &volume $1 &pitch $1
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|40 @Audio1 &vector $2 &position $2 &output $1 &pad $3 &adsr $2 &length $2 &addr $2 &volume $1 &pitch $1
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|50 @Audio2 &vector $2 &position $2 &output $1 &pad $3 &adsr $2 &length $2 &addr $2 &volume $1 &pitch $1
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|60 @Audio3 &vector $2 &position $2 &output $1 &pad $3 &adsr $2 &length $2 &addr $2 &volume $1 &pitch $1
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|80 @Controller &vector $2 &button $1 &key $1 &func $1
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|90 @Mouse &vector $2 &x $2 &y $2 &state $1 &pad $3 &scrollx $2 &scrolly $2
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|a0 @File0 &vector $2 &success $2 &stat $2 &delete $1 &append $1 &name $2 &length $2 &read $2 &write $2
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|b0 @File1 &vector $2 &success $2 &stat $2 &delete $1 &append $1 &name $2 &length $2 &read $2 &write $2
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|c0 @DateTime &year $2 &month $1 &day $1 &hour $1 &minute $1 &second $1 &dotw $1 &doty $2 &isdst $1
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```
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Varvara executes a program starting at `0x0100` until the `BRK` instruction occurs.
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`BRK` does not halt the machine (that would be `%halt { #01 LIT .System/halt DIO }`).
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Instead it signals that the present 'thread' of execution has completed, and returns control so that an interrupt handler can occur.
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The main or initialization program must register interrupt handlers before `BRK`.
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Varvara provides 'interrupt' based I/O.
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The 'vector' of a given device is a program point.
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That point will be invoked with no stack arguments when an event on the device occurs.
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Interrupt handlers execute until they terminate using the `BRK` instruction.
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Varvara enqueues interrupts and will not fire another until the one under execution has completed.
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The screen device's vector is a clock which ticks at 60hz.
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The mouse device's vector likewise fires when a mouse event such as movement or a button press occurs.
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The controller device similarly fires on input changes.
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[themes](https://wiki.xxiivv.com/site/theme.html)
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