HOW TO PLAY: Difference between revisions

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= HOW_TO_PLAY ($C00474) =
[[File:howtoplay_nam.png|thumb|A "scripted" how-to-play screen.]]


The HOW_TO_PLAY routines build a "how to play" screen.
The HOW_TO_PLAY ($C00474) [[system ROM]] call builds and animates an "how to play" screen from a command list. Only a few games use this call.


It execute the commands buffer at $10F300.
The graphics are set up using the [[fix layer]] with hardcoded tile numbers.


== Command list ==
=Command list=


Each command is always 4 bytes.
The command list must be loaded at $10F300 (how many bytes reserved ?).


The command list end with a null command ($00000000).
Each command is a longword (4 bytes):


=== Loop control ($0-$FF) ===
* The rightmost byte is the command parameter
* The next byte is the command type (0~3)
* If the command type isn't recognized, the longword is processed as being a pointer to a [[MESS OUT]] data buffer
* The end command is $00000000


Setup loop counter value or decrement current loop counter.
<pre>
00000000 00000000 000000TT PPPPPPPP
</pre>


Every between a counter setup and a counter decrement is looped until the counter reaches $00.
==Type 0: Loop control==


$FF decrement the current counter, other value setup the counter.
* If the parameter byte is less than $FF: Set a loop counter to that value
* If the parameter byte is equal to $FF: Decrement the loop counter and loop back to the previous setup command until it reaches 0


=== Arrow data ($100-$1FF) ===
==Type 1: Joystick state==


Set the color of each arrow.
Sets the color of each joystick direction arrow.


1 = light blue (pressed)
* 1 is light blue (pressed)
 
* 0 is dark blue (released)
0 = dark blue (released)


{{8BitRegister
{{8BitRegister
Line 46: Line 51:
}}
}}


If followed by a null command ($0.l) the next word contain a number of frame to wait before executing new commands.
If followed by a null command ($0.l) the next 16-bit word specifies a number of frames to wait before executing the next command.
 
=== Buttons data ($200-$2FF) ===


Set the state of each buttons.
==Type 2: Buttons state==


1 = pressed
Sets the state of each button.


0 = released
* 1 is pressed
* 0 is released


{{8BitRegister
{{8BitRegister
|0
| -
|4
|4
|A
|D
|1
|C
|1
|1
|B
|B
|1
|1
|C
|A
|1
|D
|1
|1
}}
}}


If followed by a null command ($0.l) the next word contain a number of frame to wait before executing new commands.
If followed by a null command ($0.l) the next 16-bit word specifies a number of frames to wait before executing the next command.
 
==Any other type: Text update==
 
The longword value is a pointer to a [[MESS_OUT]] data buffer.
 
This command is '''always''' followed by a 16-bit word value which specifies a number of frames to wait before executing the next command.


=== Text ===
=Example=


Pointer to a [[MESS_OUT]] data buffer.
[[NAM-1975]] sets up the following command list:


Always followed by a word value which specify the number of frame to wait before executing new commands.
<pre>
0000 0200    All buttons released
0000 01FF    All arrows highlighted
0010 F3E2    MESS_OUT write "NAM 1975" "CONTROL HERO AND CURSOR"
0004        Wait 4 frames
0000 000C    Init loop counter to 12
0000 0100    All arrows cleared      <--------------,
0000 0000    Wait...                                |
0008        ...8 frames                            |
0000 01FF    All arrows highlighted                  |
0000 0000    Wait...                                |
0008        ...8 frames                            |
0000 00FF    Loop back (blink all arrows 12 times) --'
0000 0201    A button is pressed
0000 0100    All arrows cleared
0010 F418    MESS_OUT write "MACHINE GUN"
0004        Wait 4 frames
0000 000C    Init loop counter to 12
0000 0200    All buttons released    <--------------,
0000 0000    Wait...                                |
0008        ...8 frames                            |
0000 0201    A button is pressed                    |
0000 0000    Wait...                                |
0008        ...8 frames                            |
0000 00FF    Loop back (blink A button 12 times) ----'
...
</pre>


= List of games known to use HOW_TO_PLAY =
=List of games known to use HOW_TO_PLAY=


* [[NAM-1975]]
* [[NAM-1975]]
* [[Baseball Stars Professional]]
* [[Baseball Stars Professional]]
* [[Mahjong Kyo Retsuden]]
* [[Mahjong Kyo Retsuden]]
* ...
=Tilemap=
[[File:howtoplay_tilemap.png|thumb|how-to-play tilemap, with each 8x16 block turned into the low-byte of it's hex address]]
The tiles that make up the HOW_TO_PLAY screen are found in pages 7 and 8 of the Fix rom. Much like how MESS OUT handles 8x16 text, each tile in page 7 has a counterpart at the same position on page 8, which gets displayed immediately below. (The exception to this is the black tiles around the edges, which are all 0x07FF.)<br \>
Given this unifom layout of adjacent rows, the below table combines each pair and lists only the low byte.
The interior of the lower text area is initialized with rows of 0x9920 and 0x9A20; the 8x16 spaces from fontset 9, in palette 9.
{|class="wikitable"
|+Overall Layout
|-
|FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF||FF
|-
|FF||00||01||04||05||05||05||05||05||05||05||05||05||05||05||05||05||05||05||06||07||07||07||07||07||07||07||07||07||07||07||07||07||07||07||07||07||07
|-
|FF||02||03||08||09||09||09||09||09||09||09||09||09||09||09||09||09||09||09||0A||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B||0B
|-
|FF||03||03||0C||0D||0E||0F||10||11||12||13||14||15||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||0F||63||64||65
|-
|FF||03||03||0C||5C||5D||5D||16||17||18||19||1A||1B||5D||5D||5D||5D||5D||5D||5D||5D||2C||2D||2E||2F||30||31||32||33||34||35||36||37||5D||5D||5D||5D||5D
|-
|FF||03||03||0C||5D||5D||5D||1C||1D||1E||1F||20||21||5D||5D||5D||5D||5D||38||39||3A||3B||3C||3D||3E||3F||40||41||42||43||44||45||46||5D||5D||5D||5D||5D
|-
|FF||03||03||0C||5E||5D||5D||22||23||24||25||26||27||5D||5D||5D||5D||5D||47||48||49||4A||4B||4C||4D||4E||4F||50||51||52||53||54||55||5D||5D||5D||5D||5D
|-
|FF||03||03||0C||5F||5D||5D||5D||28||29||2A||2B||5D||5D||5D||5D||5D||5D||56||57||58||59||59||59||59||59||59||59||59||59||59||5A||5B||5D||5D||5D||5D||5D
|-
|FF||68||69||0C||60||61||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||62||66||67
|-
|FF||6A||6B||6C||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||6D||76||77||77||77
|-
|FF||03||03||6F||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||78||79||79||79
|-
|FF||6E||03||70||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||7A||7B||7B||7B
|-
|FF||72||73||71||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||20||7C||7D||7D||7D
|-
|FF||FF||FF||74||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||75||7E||FF||FF||FF
|}
* The joystick (10-2B) uses palette 0x0, which changes to highlight the directions.
** Within palette 0x0, colors 5-C map to the joystick directions, starting at Up and rotating anticlockwise.
** Note: the top-halves of tiles 10-15 are in palette 0xD instead.
* The buttons (2C-5B) use palette 0xA when dim, and 0xB when illuminated.
** A tiles: 38-3B, 47-4B, 56-58
** B tiles: 2C-2F, 3C-3E, 4C-4D
** C tiles: 30-33, 3F-42, 4E-51
** D tiles: 34-37, 43-46, 52-55
** tiles 59-5B are drawn in the dim palette and never turn bright
* The text-boxes frames (04-06, 08-0A, 6C-6D, 6F-71, 74-76, 78, 7A, 7C, 7E) have palette 0xC.
* The rest of the control panel uses palette 0xD.


[[Category:Code]]
[[Category:BIOS calls]]
[[Category:BIOS calls]]

Latest revision as of 04:39, 3 March 2021

A "scripted" how-to-play screen.

The HOW_TO_PLAY ($C00474) system ROM call builds and animates an "how to play" screen from a command list. Only a few games use this call.

The graphics are set up using the fix layer with hardcoded tile numbers.

Command list

The command list must be loaded at $10F300 (how many bytes reserved ?).

Each command is a longword (4 bytes):

  • The rightmost byte is the command parameter
  • The next byte is the command type (0~3)
  • If the command type isn't recognized, the longword is processed as being a pointer to a MESS OUT data buffer
  • The end command is $00000000
00000000 00000000 000000TT PPPPPPPP

Type 0: Loop control

  • If the parameter byte is less than $FF: Set a loop counter to that value
  • If the parameter byte is equal to $FF: Decrement the loop counter and loop back to the previous setup command until it reaches 0

Type 1: Joystick state

Sets the color of each joystick direction arrow.

  • 1 is light blue (pressed)
  • 0 is dark blue (released)
Bit 7 6 5 4 3 2 1 0
Def Up-Right Right Down-Right Down Down-Left Left Up-Left Up

If followed by a null command ($0.l) the next 16-bit word specifies a number of frames to wait before executing the next command.

Type 2: Buttons state

Sets the state of each button.

  • 1 is pressed
  • 0 is released
Bit 7 6 5 4 3 2 1 0
Def - D C B A

If followed by a null command ($0.l) the next 16-bit word specifies a number of frames to wait before executing the next command.

Any other type: Text update

The longword value is a pointer to a MESS_OUT data buffer.

This command is always followed by a 16-bit word value which specifies a number of frames to wait before executing the next command.

Example

NAM-1975 sets up the following command list: 

0000 0200    All buttons released
0000 01FF    All arrows highlighted
0010 F3E2    MESS_OUT write "NAM 1975" "CONTROL HERO AND CURSOR"
0004         Wait 4 frames
0000 000C    Init loop counter to 12
0000 0100    All arrows cleared       <--------------,
0000 0000    Wait...                                 |
0008         ...8 frames                             |
0000 01FF    All arrows highlighted                  |
0000 0000    Wait...                                 |
0008         ...8 frames                             |
0000 00FF    Loop back (blink all arrows 12 times) --'
0000 0201    A button is pressed
0000 0100    All arrows cleared
0010 F418    MESS_OUT write "MACHINE GUN"
0004         Wait 4 frames
0000 000C    Init loop counter to 12
0000 0200    All buttons released     <--------------,
0000 0000    Wait...                                 |
0008         ...8 frames                             |
0000 0201    A button is pressed                     |
0000 0000    Wait...                                 |
0008         ...8 frames                             |
0000 00FF    Loop back (blink A button 12 times) ----'
...

List of games known to use HOW_TO_PLAY

Tilemap

how-to-play tilemap, with each 8x16 block turned into the low-byte of it's hex address

The tiles that make up the HOW_TO_PLAY screen are found in pages 7 and 8 of the Fix rom. Much like how MESS OUT handles 8x16 text, each tile in page 7 has a counterpart at the same position on page 8, which gets displayed immediately below. (The exception to this is the black tiles around the edges, which are all 0x07FF.)
Given this unifom layout of adjacent rows, the below table combines each pair and lists only the low byte.

The interior of the lower text area is initialized with rows of 0x9920 and 0x9A20; the 8x16 spaces from fontset 9, in palette 9.

Overall Layout
FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
FF 00 01 04 05 05 05 05 05 05 05 05 05 05 05 05 05 05 05 06 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07
FF 02 03 08 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 0A 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B 0B
FF 03 03 0C 0D 0E 0F 10 11 12 13 14 15 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 0F 63 64 65
FF 03 03 0C 5C 5D 5D 16 17 18 19 1A 1B 5D 5D 5D 5D 5D 5D 5D 5D 2C 2D 2E 2F 30 31 32 33 34 35 36 37 5D 5D 5D 5D 5D
FF 03 03 0C 5D 5D 5D 1C 1D 1E 1F 20 21 5D 5D 5D 5D 5D 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43 44 45 46 5D 5D 5D 5D 5D
FF 03 03 0C 5E 5D 5D 22 23 24 25 26 27 5D 5D 5D 5D 5D 47 48 49 4A 4B 4C 4D 4E 4F 50 51 52 53 54 55 5D 5D 5D 5D 5D
FF 03 03 0C 5F 5D 5D 5D 28 29 2A 2B 5D 5D 5D 5D 5D 5D 56 57 58 59 59 59 59 59 59 59 59 59 59 5A 5B 5D 5D 5D 5D 5D
FF 68 69 0C 60 61 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 66 67
FF 6A 6B 6C 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 6D 76 77 77 77
FF 03 03 6F 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 78 79 79 79
FF 6E 03 70 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 7A 7B 7B 7B
FF 72 73 71 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 7C 7D 7D 7D
FF FF FF 74 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 7E FF FF FF
  • The joystick (10-2B) uses palette 0x0, which changes to highlight the directions.
    • Within palette 0x0, colors 5-C map to the joystick directions, starting at Up and rotating anticlockwise.
    • Note: the top-halves of tiles 10-15 are in palette 0xD instead.
  • The buttons (2C-5B) use palette 0xA when dim, and 0xB when illuminated.
    • A tiles: 38-3B, 47-4B, 56-58
    • B tiles: 2C-2F, 3C-3E, 4C-4D
    • C tiles: 30-33, 3F-42, 4E-51
    • D tiles: 34-37, 43-46, 52-55
    • tiles 59-5B are drawn in the dim palette and never turn bright
  • The text-boxes frames (04-06, 08-0A, 6C-6D, 6F-71, 74-76, 78, 7A, 7C, 7E) have palette 0xC.
  • The rest of the control panel uses palette 0xD.
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