| CPU_Math.i | |
| Macros | |
| mulu | Unsigned multiplication (S-CPU MMIO) |
| divu | Unsigned division (S-CPU MMIO) |
| muls | Signed multiplication (S-PPU MMIO) |
Unsigned multiplication (S-CPU MMIO)
If :out: parameter is omitted, get result in RDMPYL/H (uint16) after 5 cycles
:in: n1 Multiplicand (uint8) a/x/y Requires RW a8 or i8 12 | constant Uses a, sets RW a8 13 | :in: n2 Multiplier (uint8) a/x/y Requires RW a8 or i8 14 | constant Uses a, sets RW a8 15 | :out?: ret Product (uint16) a/x/y Sets RW a16 or i16
lda #$88 16 | mulu a,$7f, x ;Returns x = #$4378
Unsigned division (S-CPU MMIO)
If :out: parameters are omitted, get quotient in RDDIVL (uint16) and remainder in RDMPYL (uint16) after 13 cycles
:in: n1 Dividend (uint16) a/x/y Requires RW a16 or i16 19 | constant Uses x, sets RW i16 20 | :in: n2 Divisor (uint8) a/x/y Requires RW a8 or i8 21 | constant Uses a, sets RW a8 22 | :out?: ret Quotient (uint16) a/x/y Sets RW a16 or i16 23 | :out?: retr Remainder (uint16) a/x/y Sets RW a16 or i16
Signed multiplication (S-PPU MMIO)
Not available during Mode 7 rendering If :out: parameter is omitted, result available in MPYL/M/H (sint24) immediately
:in: n1 Multiplicand (sint16) x/y Uses a, sets RW a8 26 | constant Uses a, sets RW a8 27 | :in: n2 Multiplier (sint8) a Requires RW a8 28 | constant Uses a, sets RW a8 29 | :out?: ret Product (sint24) ax/ay Sets RW a8i16
Map.cfg is the configuration file passed to the ld65 linker.
It consists of two main parts∶
In include/Configurations there are several template configuration files for different ROM sizes and memory layouts.
For full documentation of ld65 and its configuration refer to the official documentation.
Optional package adding SNES SFM1 Mouse support
To link mouse support in a project, simply add Mouse to libsfx_packages in the project makefile.
# Use packages 8 | libsfx_packages := Mouse
The mouse package adds mouse polling to the regular automatic joypad polling. By default the driver will look for a mouse in port 1. This is configurable with the SFX_MOUSE variable∶
SFX_MOUSE = MOUSE1 | MOUSE2
Mouse read-out data is stored in MOUSE_data structs with the following members∶
.struct MOUSE_data 9 | status .byte 10 | sensitivity .byte 11 | buttons_cont .byte 12 | buttons_trig .byte 13 | delta_x .byte 14 | delta_y .byte 15 | cursor_x .word 16 | cursor_y .word 17 | .endstruct 18 | 19 | Possible status values: 20 | .define MOUSE_status_nc $00 ;Mouse not connected 21 | .define MOUSE_status_ok $01 ;Mouse connected and working 22 | .define MOUSE_status_error $80 ;Hardware error 23 | 24 | Button presses are stored in the follwing bits of buttons_cont/buttons_trig: 25 | Bit 26 | 7 Right button 27 | 6 Left button
The driver updates all members during each VBlank interval at zero page locations SFX_mouse1 and SFX_mouse2. The data can be addressed like this∶
;Load cursor vertical position 28 | lda z:SFX_mouse1+MOUSE_data::cursor_y
The ‘sensitivity’ member is used to set the mouse acceleration curve.
;Set normal mouse sensitivty 29 | lda #MOUSE_sensitivity_normal 30 | sta SFX_mouse1+MOUSE_data::sensitivity 31 | 32 | ;Possible values 33 | .define MOUSE_sensitivity_slow 0 34 | .define MOUSE_sensitivity_normal 1 35 | .define MOUSE_sensitivity_fast 2
All other members are read-only.
If no mouse is detected and SFX_JOY is set for the port, the driver automatically falls back to joypad input. D-pad input is then mapped to delta and cursor, and the A/X buttons is mapped to the left/right buttons.
The driver can optionally be “hugged” by special strings that – I suppose – some emulators rely on to automatically enable mouse input. Real hardware (and consequently, real emulators) doesn’t care.
SFX_MOUSE_STRINGS = ENABLE
| SMP_Util.i | |
| Macros | |
| DSP_get | Get DSP register |
| DSP_set | Set DSP register |
| SMP_exit | Return to IPL (clears timers, zeropage) |
libSFX is a Super Nintendo assembler development framework. It aims to add as little magic and abstraction to the programming as possible while removing the tedium of boilerplate and mandatory micro management of configuration files.
By leveraging the ca65 assembler and several macro packs it can create object code for∶
Using (and optionally extending) the included makefiles and configurations it’s a relative breeze to get SNES code up and running!
Anatomy libSFX consists of a small runtime that mainly initializes the system and handles hardware interrupts (which can be redirected in software). The real rice of the library are the macros included and documented here.
Packages There are also opt-in packages, adding a bit more to the object code size, for non-core features like input peripherals and data decompression. These are documented in the “Packages” section.
Tools The ca65 toolchain and a couple of support tools are included as submodules in the libSFX/tools directory. These are the only tools used by the libSFX.make makefile, making libSFX pretty much self contained. Running make from the repository root will sync the submodules and build the tools.
SFX 🤷️ Why is it called libSFX? That sounds like a library of sound effects. Well, yes it does. However, “SFX” was also how Nintendo refered to the SNES/SFC in the very early developer documentation. It was through photocopied binders of those documents – with severe generation loss! – I first learned about the innards of the Super Nintendo, and I have lovingly cultivated a habit of using SFX to prefix and suffix my SNES code over the years.
Get started Clone, fork or download the repository at github.com/Optiroc/libSFX and dive into the Make documentation.
libSFX is developed by David Lindecrantz and distributed under the terms of the MIT license.