Video In to AXI4-Stream
19
PG043 April 24, 2012
General Design Guidelines
Clocking
There are two clocks used in this core.
• Video input pixel clock
• AXI4-Stream clock
The video input clock corresponds to the video line standard used on the input. It is part of
the video line standard and is used by both the Video In to AXI4-Stream core and by the
corresponding Video Timing Controller core that is used to detect video timing.
The AXI4-Stream clock (aclk) is part of the AXI4-Stream bus. To minimize buffering
requirements, this clock should be of equal or higher frequency than the video input clock.
This clock can be slower than the video input clock, in which case, additional buffering is
required to store pixels so that lines can be input at the burst rate of the video clock. This
is discussed in the
section. At a minimum, the aclk frequency must be
higher than the average pixel rate.
Resets
There are two external resets provided: rst, which resets the entire core, and aresetn, which
resets the AXI4-Stream interface. Both resets cause the FIFO to be reset. When asserted, the
reset should be held for least two clock periods of the lowest frequency clock.
X-Ref Target - Figure 4-1
Figure 4-1:
Example of ACLK Routing and AXI4-Stream Interconnect
S?AXIS?VIDEO?TDATA
S?AXIS?VIDEO?TVALID
S?AXIS?VIDEO?TREADY
S?AXIS?VIDEO?TLAST
S?AXIS?VIDEO?TUSER
ACLK
ACLKEN
ARESETN
M?AXIS?VIDEO?TDATA
M?AXIS?VIDEO?TVALID
M?AXIS?VIDEO?TREADY
M?AXIS?VIDEO?TLAST
M?AXIS?VIDEO?TUSER
6IDEO)0 h3OURCE v
S?AXIS?VIDEO?TDATA
S?AXIS?VIDEO?TVALID
S?AXIS?VIDEO?TREADY
S?AXIS?VIDEO?TLAST
S?AXIS?VIDEO?TUSER
VTG?ACT?VID
VTG?HSYNC
VTG?VBLANK
VTG?HBLANK
VTG?VSYNC
VIDEO?DATA
VIDEO?DE
VIDEO?VSYNC
VIDEO?HSYNC
VIDEO?VBLANK
VIDEO?HBLANK
VTG?CE
!8)3TREAMTO6IDEO/UT
ACLKEN
ACLK
ARESETN
ACTIVE?VIDEO?OUT
VBLANK?OUT
HBLANK?OUT
VSYNC?OUT
HSYNC?OUT
6IDEO4IMING#ONTROLLER GENERATOR
GEN?CLKEN
ACLK
ACLKEN
ARESETN