AMD Geode SC1201 - Manual (Page 316)

316 AMD Geode™ SC1200/SC1201 Processor Data Book
Video Processor Module 32579B
7.2.1.1 Direct Video Mode
As stated previously, Direct Video mode is on by default so
no registers need to be programmed to support this mode
other than to select the direct video data at the video mux.
The video mux control register is located at F4BAR0+Mem-
ory Offset 400h[1:0].
GenLock
Because video input data from the VIP is sent directly, with-
out significant buffering, field-to-field synchronization is
required with the TV encoder, and frame-to-field synchroni-
zation is required with the GX1 module’s graphics data.
This synchronization is known as GenLock. The GenLock
registers are located at F4BAR0+Memory Offset 420h and
424h.
The odd/even fields of the video input data must be syn-
chronized with the odd/even fields produced by the TV
encoder. This field-to-field synchronization is accomplished
by setting the SG_GENLOCK_EN bit (F4BAR0+Memory
Offset 420h[0]). Field-to-field synchronization is only
required once.
The GenLock control hardware is used to synchronize the
video input’s field with the GX1 module’s graphics frame.
The graphics data is always sent full frame. For the Gen-
Lock function to perform correctly, the GX1 module’s Dis-
play Controller must be programmed to have a slightly
faster frame time then the video input’s field time. This is
best accomplished by programming the GX1 module’s Dis-
play Controller with a few less (three to five) horizontal lines
then the VIP interface. GenLock is accomplished by stop-
ping the clock driving the GX1 module’s graphics frame
until the VIP vertical sync occurs (plus some additional
delay, via F4BAR0+Memory Offset 424h).
The GenLock function provides a timeout feature
(GENLOCK_TOUT_EN, F4BAR0+Memory Offset 420h[4])
in case the video port input clock stops due to a problem
with incoming video.
7.2.1.2 Direct VBI Mode
Direct VBI mode operation is very similar to Direct Video
mode and is also on by default. The VBI mux control is
located at F4BAR0+Memory Offset 400h[2]. Specific VBI
lines may be blocked or nulled before they are sent to the
TV Encoder, (F4BAR2+Memory Offsets 18h and 1Ch). VBI
GenLock is also required for Direct VBI mode to perform
correctly. See Section 7.2.1.1 for a more detailed explana-
tion on GenLock.
7.2.1.3 Capture Video Mode
Capture Video mode is a process for bus mastering Video
data received from the VIP block to the GX1 module’s
Video Frame Buffer. The GX1 module’s Display Controller
then moves the data from the Video Frame Buffer to the
Video Formatter. Usually Capture Video mode is used
because the data coming in from the VIP block is interlaced
and has a 30 Hz refresh rate (NTSC format) and the output
device, CRT monitor or TFT panel, is progressive and has
a 60 to 85 Hz refresh rate. The Capture Video mode pro-
cess must convert the interlaced data to progressive data
and change the frames per second. There are two methods
to perform the interlaced to progressive conversion; Bob
and Weave. Each method uses a different mechanism to
up the refresh rate.
Table 7-1. Direct Mode and Capture Mode Configurations
Video
Mode
VBI
Mode
Output
Interface Comments
Direct Direct TV Video data must be full frame. GX1 graphics/video frame buffers are not used.
Direct Capture TV Video data must be full frame. VBI data can be decoded, turned into graphic
information and placed in the GX1 module’s graphics frame buffer for display,
or it can be manipulated and placed into the video frame buffer as modified VBI
data.
Capture Direct TV Unsupported
Capture Capture TV, CRT,
TFT
The only mode available for CRT and TFT displays and only necessary for TV
displays when video data is less then full frame. CRT and TFT displays do not
allow for VBI at all. However, VBI data can be decoded, turned into graphic
information and placed in the GX1 module’s graphics frame buffer for display.
Restriction: The GX1 module’s video frame buffer cannot be used to send both
video and VBI data.