I2C(also IIC; the "2" is superscripted) Inter-Integrated Circuit Bus -- A moderate-speed serial communications bus originally invented by Philips in the early 1980s for consumer-electronics applications, such as inter-chip communication in a television set or high-end stereo. The I2C bus has recently appeared on PCs in video capture boards and similar devices, as well as (surprisingly) SDRAM DIMMs (for the on-board serial EEPROM). The ACCESS.bus is a derivative of the I2C bus which forms the physical layer of the Universal Serial Bus. Similary, the SMBus (System Management Bus) also uses I2C as its physical layer. 86h/D8h - ITT VPX 32xx - VREF/HREF Control Bitfields for VPX 32xx VREF/HREF control: Bit(s) Description (Table I0036) 0 reserved 1 HREF polarity (=0 active high, =1 active low) 2 VREF polarity (=0 active high, =1 active low) 5-3 length of HREF pulse (+2 clocks) 6 PREF select 0 odd/even flag 1 Pintr (programmable interrupt) 7 PREF polarity (=1 invert polarity) Note: the Stealth64 Video 2001TV uses the PREF output to control the audio signal; set bit 6 to select programmable interrupt on PREF, then set bit 7 to mute, clear bit 7 to enable sound