The following screen modes are available: Mode 0: 640 x 256 2-colour graphics and 80 x 32 text (20K) Mode 1: 320 x 256 4-colour graphics and 40 x 32 text (20K) Mode 2: 160 x 256 16-colour graphics and 20 x 32 text (20K) Mode 3: 80 x 25 2-colour text only (16K) Mode 4: 320 x 256 2-colour graphics and 40 x 32 text (10K) Mode 5: 160 x 256 4-colour graphics and 20 x 32 text (10K) Mode 6: 40 x 25 2-colour text only (8K) Mode 7: 40 x 25 Teletext display (1K) Mode 128: 640 x 256 2-colour graphics and 80 x 32 text (20K) Mode 129: 320 x 256 4-colour graphics and 40 x 32 text (20K) Mode 130: 160 x 256 16-colour graphics and 20 x 32 text (20K) Mode 131: 80 x 25 2-colour text only (16K) Mode 132:
320 x 256 2-colour graphics and 40 x 32 text (10K) Mode 133: 160 x 256 4-colour graphics and 20 x 32 text (10K) Mode 134: 40 x 25 2-colour text only (8K) Mode 135: 40 x 25 Teletext display (1K) All graphics access is transparent. Shadow mode gives 32K BASIC program RAM (less workspace) to the user in any screen mode. The shadow screen mode offers equivalent display sizes to the standard mode 0 to 7 screens, but using an auxiliary memory area, the "shadow" RAM. In shadow display modes (nudes 128 to 135) BASIC or a user program is free to use all memory between OSHWM (PAGE) and &7FFF, plus the 12K bytes of sideways (paged) RAM.
The 12K paged RAM is available to the user in any screen mode, shadow or non-shadow. Serial interface to RS423 standard. The new standard has been designed to be inter-operable with RS232C equipment. Baud rates are software selectable between 75 baud and 19200 baud (guaranteed up to 9600 baud) . An 8-bit input/output port with 2 control bits. Four analogue input channels. Each channel has an input voltage range of OV to 1.8V. The conversion time for each channel is 10 milliseconds. The resolution of the ADC chip is 10 bits. 1 MHz buffered extension bus for connection to a variety of external hardware such as a TELETEXT acquisition unit, IEEE 488 interface, WINCHESTER disc drive etc.
Buffered interface for connection via the TUBE to a range of second processors. CENTRONICS compatible printer interface. The basic model B+ may have added to it a floppy disc interface using either an 8271 or 1770 controller IC. Also, a low cost network interface, the Acorn ECONET, may be added. Finally, a speech upgrade is available using the 5220 speech IC to generate predefined words and sounds through the built-in speaker. 4