BBC Micro

BBC Micro / Acorn Electron

The Acorn 8-bit systems consist of a 6502 processor @ 2MHz (65SC12 in Master 128) with a 6845 CRTC for bitmap graphics, SAA5050 for teletext graphics, and a TI SN76489 sound chip.

Setting up

To set up your , first get the following tools:

• Assembler: BeebAsm ( https://github.com/stardot/beebasm )
• Emulator(s): BeebEm, b2 ( http://www.mkw.me.uk/beebem/ ) ( https://github.com/tom-seddon/b2 )

Memory map

0000 	Current Language Zero Page 
0090 	Operating System Zero Page
0100 	Processor Stack
0200 	Operating System Workspace
0300
0400 	Current Language Workspace
0500
0600
0700
0800 	Sound & Printer Buffer
0900 	RS423, Speech & Tape output Buffer
0A00 	RS423 & Tape input Buffer
0B00 	Function Keys
0C00 	User defined graphics
0D00 	NMI routines (Disk/Econet)
0D9F 	Expander vector set
0DF0 	Paged ROM workspace storage locations
0E00 	USER workspace 	/ DFS workspace (not Master)
...
3000 	Screen (Mode 0, 1, 2) 	USER workspace with shadow Mode 128…134
4000 	Screen (Mode 3)
5800 	Screen (Mode 4, 5)
6000 	Screen (Mode 6)
7B00 	Screen (Mode 7)
C000 	OS ROM 	Paged rom workspace
DC00 	MOS CLI Buffer
DD00 	*MOVE workspace
DF00 	MOS private workspace
E000 	OS ROM
FC00 	FRED 1MHz bus
FD00 	JIM 1MHz bus
FE00 	SHIELA I/O Memory
FF00 	OS ROM Vectors

Check out https://mdfs.net/Docs/Comp/BBC/AllMem for a complete memory map

Video display

The BBC Micro / Acorn Electron have the following native video modes:

• Standard text modes
• Bitmap modes
• Teletext / Mode 7 (BBC Micro only)

Sync with frame

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Plot in Bitmap modes

Here is a routine that will allow you to plot a single point in bitmap mode.

To be added

Text mode

To be added

To be added

Sound

To be added soon.

Make some noise

To be added soon.

Additional Resources

• Stardot forums https://stardot.org.uk/forums/