PIN FUNCTION DESCRIPTION (Continued)
Read control input (TTL compatible). To read data from the device, RD must be a logical zero. RS0–RS2 are
latched on the falling edge of RD during MPU read operations.
RS0, RS1, RS2 Register select inputs (TTL compatible). RS0–RS2 specify the type of read or write operation being performed as
illustrated in Tables I and II.
Data bus (TTL compatible). Data is transferred into and out of the device over this 8-bit bidirectional data bus.
D0 is the least significant bit.
8-bit/6-bit select input (TTL compatible). This control input specifies whether the MPU is reading and writing 8-
bits (logical one) or 6-bits (logical zero) of color information each cycle. For 8-bit operation, D7 is the most sig-
OBSOLETE nificant data bit during color read/write cycles. For 6-bit operation, D5 is the most significant data bit during color
read/write cycles (D6 and D7 are ignored during color write cycles and are logical zero during color read cycles).
This control input is implemented only on the ADV478.
The level separating the SYNC portion from the video portion
of the waveform. Usually referred to as the front porch or back
porch. At 0 IRE units, it is the level which will shut off the pic-
ture tube, resulting in the blackest possible picture.
Color Video (RGB)
This usually refers to the technique of combining the three pri-
mary colors of red, green and blue to produce color pictures
within the usual spectrum. In RGB monitors, three DACs
would be required, one for each color.
Composite SYNC Signal (SYNC)
The portion of the composite video signal which synchronizes
The most basic method of sweeping a CRT one line at a time to
generate and display images.
Reference Black Level
The maximum negative polarity amplitude of the video signal.
Reference White Level
The maximum positive polarity amplitude of the video signal.
The difference between the reference black level and the blank-
The peak level of the composite SYNC signal.
the scanning process.
Composite Video Signal
The video signal with or without setup, plus the composite
That portion of the composite video signal which varies in gray
scale levels between reference white and reference black. Also
referred to as the picture signal, this is the portion which may be
The discrete levels of video signal between reference black and
reference white levels. An 8-bit DAC contains 256 different lev-
els while a 6-bit DAC contains 64.