tsvm/terranmon.txt

1 byte = 2 pixels

560x448@4bpp = 125 440 bytes
560x448@8bpp = 250 880 bytes

-> 262144 bytes (256 kB)

[USER AREA | HW AREA]

    Number of pheripherals = 8, of which the computer itself is considered as
     a peripheral.

HW AREA = [Peripherals | MMIO | INTVEC]

User area: 8 MB, hardware area: 8 MB

8192 kB
    User Space
1024 kB
    Peripheral #8
1024 kB
    Peripheral #7
...
1024 kB  (where Peripheral #0 would be)
    MMIO and Interrupt Vectors
    128 kB
        MMIO for Peri #8
    128 kB
        MMIO for Peri #7
    ...
    128 kB  (where Peripheral #0 would be)
        MMIO for the computer
        130816 bytes
            MMIO for Ports, etc.
        256 bytes
            Vectors for 64 interrupts

--------------------------------------------------------------------------------

IO Device

Endianness: little
Note: Always takes up the peripheral slot of zero

Latching: latching is used to "lock" the fluctuating values when you attempt to read them so you would get
          reliable values when you try to read them, especially the multibyte values where another byte would
          change after you read one byte, e.g. System uptime in nanoseconds

MMIO

0..31 RO: Raw Keyboard Buffer read. Won't shift the key buffer
32..33 RO: Mouse X pos
34..35 RO: Mouse Y pos
36 RO: Mouse down? (1 for TRUE, 0 for FALSE)
37 RW: Read/Write single key input. Key buffer will be shifted. Manual writing is
    usually unnecessary as such action must be automatically managed via LibGDX
    input processing.
    Stores ASCII code representing the character, plus:
    19: Up arrow
    20: Down arrow
    21: Left arrow
    22: Right arrow
38 RW: Request keyboard input be read (TTY Function). Write nonzero value to enable, write zero to
    close it. Keyboard buffer will be cleared whenever request is received, so
    MAKE SURE YOU REQUEST THE KEY INPUT ONLY ONCE!
39 WO: Latch Key/Mouse Input (Raw Input function). Write nonzero value to latch.
    Stores LibGDX Key code
40..47 RO: Key Press buffer
    stores keys that are held down. Can accomodate 8-key rollover (in keyboard geeks' terms)

64..67 RO: User area memory size in bytes
68 WO: Counter latch
    0b 0000 00ba
    a: System uptime
    b: RTC
72..79 RO: System uptime in nanoseconds
80..87 RO: RTC in microseconds

4084..4091 RO: Block transfer status
    0b nnnnnnnn a000 mmmm

    n-read: size of the block from the other device, LSB (4096-full block size is zero)
    m-read: size of the block from the other device, MSB (4096-full block size is zero)
    a-read: if the other device hasNext (doYouHaveNext), false if device not present

    n-write: size of the block I'm sending, LSB (4096-full block size is zero)
    m-write: size of the block I'm sending, MSB (4096-full block size is zero)
    a-write: if there's more to send (hasNext)

4092..4095 RW: Block transfer control for Port 1 through 4
    0b 00ms abcd

    m-readonly: device in master setup
    s-readonly: device in slave setup

    a: 1 for send, 0 for receive

    b-write: 1 to start sending if a-bit is set; if f-bit is unset, make other device to start sending
    b-read: if this bit is set, you're currently receiving something (aka busy)

    c-write: I'm ready to receive
    c-read: Are you ready to receive?

    d-read: Are you there? (if the other device's recipient is myself)

    NOTE: not ready AND not busy (bits b and d set when read) means the device is not connected to the port

4096..8191 RW: Buffer for block transfer lane #1
8192..12287 RW: Buffer for block transfer lane #2
12288..16383 RW: Buffer for block transfer lane #3
16384..20479 RW: Buffer for block transfer lane #4

--------------------------------------------------------------------------------

VRAM Bank 0 (256 kB)

Endianness: little

From the start of the memory space:
250880 bytes
    Framebuffer
3 bytes
    *reserved for future use*
1 byte
    command (writing to this memory address changes the status)
        1: reset palette to default
        2: fill framebuffer with given colour (arg1)
2 bytes
    argument for "command" (arg1: Byte, arg2: Byte)
    write to this address FIRST and then write to "command" to execute the command
86 bytes
    *Unused*
IF graphics_mode THEN
    (41 sprites : 260 bytes each -> 10660 bytes)
        0th sprite is always the GUI cursor
    2 bytes
        Ob hv0000xy yyyyyyyy (h: horizontal flip, v: vertical flip, x: show/hide, y: y-position)
    2 bytes
        0b rr0000xx xxxxxxxx (r: rotation, x: x-position)
    256 bytes
        16x16 texture for the sprite
ELSE
    2978 bytes
        *Unused*
    2 bytes
        Cursor position in: (y*32 + x)
    2560 bytes
        Text foreground colours
    2560 bytes
        Text background colours
    2560 bytes
        Text buffer of 70x32 (8x14 character size, and yes: actual character data is on the bottom)
FI
512 bytes
    Palette stored in following pattern: 0b rrrr gggg, 0b bbbb aaaa, ....
    Palette number 255 is always full transparent (bits being all zero)

MMIO

0..1 RO
    Framebuffer width in pixels
2..3 RO
    Framebuffer height in pixels
4 RO
    Text mode columns
5 RO
    Text mode rows
6 RW
    Text-mode attributes
    0b kkkk 00rc (k: currently using character rom, r: TTY Raw mode, c: Cursor blink)
7 RW
    Graphics-mode attributes
    0b 0000 000g (g: Use sprites(wipes out text buffer))
8 RO
    Last used colour (set by poking at the framebuffer)
9 RW
    current TTY foreground colour (useful for print() function)
10 RW
    current TTY background colour (useful for print() function)


Text-mode-font-ROM is immutable and does not belong to VRAM
Even in the text mode framebuffer is still being drawn onto the screen, and the texts are drawn on top of it