AMD Geode LX 800@0.9W - Manual (Page 469)

AMD Geode™ LX Processors Data Book 469
Video Input Port 33234H
6.9.5.2 Ancillary Packets
Ancillary packets are received during vertical and/or hori-
zontal blanking. The ancillary packet has a 6-byte header
of 00-FF-FF-DID-SDID-NN. The first three bytes are the
pre-amble. The DID and SDID bytes are the data identifier
and the secondary data identifier bytes. The NN byte is the
data count and specifies the length of the ancillary data
block in DWORDs (4-byte blocks). The entire ancillary data
packet is stored to memory, including all 6 bytes of pream-
ble/header. See Section 6.9.10 on page 475 for further
explanation. There is no restriction on the code in the data
section of the packet (codes 00 and FF are allowed) The
SAV/EAV packet preamble detection circuitry is disabled
during the reception of these NN blocks of data to allow
reception of 00, FF codes. The active data is received on
bits [7:0] in 8-bit mode, [9:0] in 10-bit mode and on [15:0] in
16-bit mode.
A sample ancillary packet is shown in Figure 6-42.
Figure 6-42. Ancillary Data Packets
0
0 F
F F
F D
I
S
I
N
N
6 Byte Ancillary Header
D D
First DWORD Last DWORD
I
d0 d1 d2 d d d d d
check sum
fill byte
0
0
F
F F
F D
I
S
I
D D
First Last
d0 d2 d4 d6 d d d d d
check
X X X X X X d1 d3 d5 d7 d d d d d
fill byte
d
d
DWORD
6 Byte Ancillary Header
N
N
8/10-BIT ANCILLARY PACKET
16-BIT ANCILLARY PACKET
sum
D
D
I
D
D
DWORD
VID[7:0]
VID[7:0]
VID[15:8]