MOS Technology VIC - Definition and Overview

The VIC (Video Interface Chip), specifically known as the MOS Technology 6560 (NTSC version) / 6561 (PAL version), is the integrated circuit chip responsible for generating video graphics and sound in the Commodore VIC-20 home computer. It was originally designed for applications such as low cost CRT terminals, biomedical monitors, control system displays and arcade or home video game consoles.

Its features include:

• 16 KB address space for screen, character and color memory (only 5 KB points to RAM on the VIC-20 without a hardware modification)
• 16 colors (the upper 8 can only be used in the global background and auxilary colors)
• two selectable character sizes (8×8 or 8×16 bits; the pixel width is 1 bit for "hires" characters and 2 bits for "multicolor" characters)
• maximum video resolution depends on the television system (176 × 184 is the standard for the VIC-20 firmware, although at least 224 × 256 is possible on the PAL machine)
• sound system (4 channels (3 square wave + "white" noise) + global volume setting)
• on-chip DMA
• two 8-bit A/D converters
• light pen support

The VIC was programmed by manipulating its 16 control registers, memory mapped to the range $9000–$900F in the VIC-20 address space. The on-chip A/D converters were used for dual paddle position readings by the VIC-20, which also used the VIC's lightpen facility. The VIC preceded the much more advanced VIC-II, used by the VIC-20's successors, the C64 and C128.

VIC IC list

• MOS Technology 6560 NTSC
• MOS Technology 6561E PAL Ceramic version, used in early VIC-20's
• MOS Technology 6561-101 PAL

External links

• VIC Chip info from Rick Melick's VIC-20 Tribute Page (http://www.geocities.com/rmelick/6561.txt)
• More info, incl register usage (http://www.geocities.com/rmelick/6561d.txt)