Source Codes
From CPCWiki - THE Amstrad CPC encyclopedia!
This article contains source codes and programming examples. You may also have a look at
Contents
Assembler
Algorithms
- Bubble sort
- CPC OS floating point routines
- CRC16
- CRC32
- Integer Division
- Integer Multiplication
- Logarithm
- Ultrafast Multiplication by Prodatron
- Fast Square Root
- Fast 16 bit Square Root by Executioner
- Filling memory with a byte
- Square Root
- Precalculated square
- Random Number Generator
- Reverse A
- Quicksort
- Sin/Cos calculation
CP/M
- A simple 'Hello World' program for CP/M using BDOS
- A simple 'Hello World' program for CP/M using BIOS
- Executing firmware functions from within CP/M 2.1
- Executing firmware functions from within CP/M 2.1 or CP/M plus
- Executing firmware functions from within CP/M 2.1
- Executing firmware functions from within CP/M plus
CPC Plus
- Amstrad CPC plus sprite format
- Convert CPC sprites to Plus hardware sprites
- Sprites Multiplexing
- Hardware sprites
- Horizontal scroll
- RLE hardware sprites
- Screen splitting
- Vertical scroll
- Operation of Z80 interrupt mode 0 in the CPC plus design
- Simple Raster Example 1 (uses CPC plus features)
- Simple Raster Example 2 (uses CPC plus features)
- Unlocking ASIC
Devices
File access
- An example to read a file byte-by-byte
- An example to write a file byte-by-byte
- A simple file copier using firmware functions (copies byte-by-byte)
- Loading a file
- Saving a file
- Unlocking a protected basic file
- Undo delete of file
Floppy disk
- A simple disc copier using BDOS functions
- A simple disc formatter using BDOS functions
- An example loader
- Catalog a disc and retrieve a directory
- Detecting an Amstrad or Vortex disc controler
- Formatting a track on a disc
- Reading a sector from a disc
- Reading and writing the boot sector of a SYSTEM/VENDOR disc
- Writing a sector to disc
Graphics
- Display a 8-bit number in binary
- Display a 8-bit number in hex
- Display a byte as a 3-digit decimal number
- Display and update Scores
- Distorting the screen using register 2 of the CRTC (Horizontal Sync Position)
- Fast plot
- Fast Sprites by Executioner
- Fast Textoutput by Prodatron
- Fastest Character Print in Mode 2 in all screen positions by FG Brain
- Hardware Scrolling by Executioner
- Hardware Scrolling 2
- Hardware scrolling the screen horizontally byte-by-byte using the CRTC
- Hardware scrolling the screen using the CRTC
- Next / previous line calculation
- Overscan
- Plotting a sprite using character matrices
- 4th Mode of CPCs: Plotting sprites on 2 bitplanes
- Set the screen refresh rate
- Simple Raster Example
- Simple Split Raster Example
- Synchronising with the CRTC and display
- CRTC change colour (fill) test with precise timing by Matahari
- 256 byte Overscan MEGATEXT Intro - (features 50Hz fullscreen scroll) by Matahari
Interrupts
Keyboard
Other routines
- An example boot sector (executed with rsx command CPM)
- An example to define a RSX
- Calling a RSX from outside of BASIC
- Dumping the data of BASIC or AMSDOS or an expansion rom
- Dumping the data of the lower rom
Sound
- How to access the PSG via PPI
- Tutorial - Understanding the fundamentals of BASIC SOUND and the Firmware SOUND QUEUE
- Source code to show 0x0ff is always returned when reading PSG port B
- Source code to show it is possible to store data in PSG register 14 and 15 (port A and port B)
- Source code to show it is possible to store data in PSG register 14 and 15 even if the port has been set to input
- Source code to show that some registers always return 0 in some bits
- Source code to show that when a port is read in output mode; the data read will be ANDed with the inputs to that port
Cross Development
General Notes
- Memory range for programs is &0040-&a700. This avoids firmware and memory allocated by AMSDOS disc ROM.
This is safe for the purpose of loading and being compatible with the firmware. After loading, if you disable the firmware, you can re-use the firmware areas as you want, but you need to do everything yourself (scanning keyboard, drawing, sound etc).If you need to use these areas, a common thing to do is to load most into the safe area, some into the screen, and relocate it after loading.
- Programs on cassette and disc have a header that define the load address, length and execution address.
In Pasmo assembler use the "end" mnemonic to define the label which is the execution address and use "--amsdos" to put an AMSDOS header on it.
- Basic programs start at &170.
- Firmware uses interrupt mode 1 of the Z80 (interrupts jump to &0038)
- Lowest place you can LOAD a binary file to with BASIC is &389 e.g.:
openout"d" memory <address>-1 closeout load "code",<address> call <exec>
- Screen is normally at &c000-&ffff. (It can be changed using firmware, or using CRTC R12/R13)
- Stack is normally at &c000 and goes down.
- Extra registers (BC', AF', HL', DE' are reserved by the firmware). Avoid if you are using firmware functions.
- Lower rom (containing OS) can be paged into memory between &0000-&3fff.
- Upper rom is selectable, examples are BASIC and AMSDOS. They can be paged into memory between &c000-&ffff.
- From basic, a game is run with:
RUN"<filename>
keep it in the safe memory ranges and it'll run from cassette and disc.
- Screen is normally 40 crtc chars wide (CRTC R1=40), 25 crtc chars tall (CRTC R6=25). 8 scan lines per char (R9=7). Firmware functions assume this.
- Screen is bitmapped. You must draw/erase your own sprites and text.
- Firmware refreshes the palette every 50th of a second, so you need to turn off the firmware and use the hardware directly, or set the colours using firmware.
- Firmware can be "turned off", by disabling lower ROM, redirecting interrupts and not calling firmware functions.
- Screen can be resized the same as the Spectrum. Provided you do not use hardware scrolling, this gives you extra space although because of the layout of the screen, it's not continuous, it's in 8 seperate blocks, but it's enough to store data and code.
