User guide

Chapter 3: Interfaces 3–15
Avalon-ST Video Protocol
January 2013 Altera Corporation Video and Image Processing Suite
User Guide
Example 2 (Data Transferred in Sequence)
This example shows how a number of pixels from the middle of a frame could be
processed by another MegaCore function. This time handling a color pattern that has
planes B'G'R' in sequence. This example does not show the start of packet and end of
packet signals because these are always low during the middle of a packet.
The bits per pixel per color plane and color pattern are listed in Table 3–9.
Figure 3–13 shows how a number of pixels from the middle of a frame are processed.
This example is similar to Figure 3–12 on page 3–13 except that it is configured to
accept data in sequence rather than parallel. The signals shown in the timing diagram
are therefore the same but with the exception that the two data ports are only 8 bits
wide.
The sequence of events shown in Figure 3–13 is:
1. Initially,
din_ready is logic '1'. The source driving the input port sets din_valid to
logic '1' and puts the blue color value B
m,n
on the din_data port.
2. The source holds
din_valid at logic '1' and the green color value G
m,n
is input.
3. The corresponding red color value R
m,n
is input.
4. The MegaCore function sets
dout_valid to logic '1' and outputs the blue color
value of the first processed color sample on the
dout_data port. Simultaneously
the sink connected to the output port sets
dout_ready to logic '0'. The Avalon
Interface Specifications state that sinks may set ready to logic '0' at any time, for
example because the sink is a FIFO and it has become full.
Table 3–9. Parameters for Example of Data Transferred in Sequence
Parameter Value
Bits per Color Sample 8
Color Pattern
RGB
Figure 3–13. Timing Diagram Showing R’G’B’ Transferred in Sequence
Note to Figure 3–13:
(1) The startofpacket and endofpacket signals are not shown but are always low during the sequence shown in this figure.
clock
din_ready
din_valid
din_data 7:0
R
m,n
R
G
0,0
G
m,n
B
m,n
B
m+1,n
1.
2.
3.
4.
5. 6.
7.
dout_ready
dout_valid
dout_data 7:0
R
8.
9.
G
1,0
G
m+1,n
G
0,0
G
m,n
B
m,n
m+1,n
m,n