AMD Geode LX 800@0.9W - Manual (Page 476)

476 AMD Geode™ LX Processors Data Book
Video Input Port 33234H
6.9.10.1 Video Data Buffers
Video data buffers can be organized in linear or planar for-
mats. Linear buffers pack YUV values contiguous in mem-
ory. Planar buffers have separate subbuffers for each set of
YUV values in a field or frame. The VIP Control 1 register
(VIP Memory Offset 00h[4]) determines if the video storage
format is linear or planar.
In linear format, the first video line is stored beginning at
the vid_base address, the second line is stored beginning
at vid_base + pitch, the third line at task_base + (2 x pitch)
and so on until the end of the field/frame. See Figure 6-51
on page 477 for an example of a 4:2:2 SAV/EAV packets
stored in system memory in a linear format.
In planar format, the Y buffer begins at the task_base
address, the U buffer begins at the (vid_base +
U_buffer_offset), and the V values start at the (vid_base +
V_buffer_offset). The pitch value for Y is vid_pitch. The
pitch value for V and U is task_A_UV_pitch (for Task A UV
data) or task_b_pitch/2 (Task b UV data). In 4:2:2 or 4:2:0
video, there are twice as many Y data values per line as
there are U or V values. Additional odd/even offsets and
pitch registers are provided for Task A data. Input U/V val-
ues can be decimated (even lines or even fields). This fur-
ther reduces the U and V data to 1/4 of the Y data.
See Figure 6-51 on page 477 and Figure 6-52 on page 478
for examples of SAV/EAV packets stored in linear buffer
and planar buffer format.
6.9.10.2 VBI Data Buffers
The VBI data packets are stored in linear format. VBI data
is essentially a line of video that occurs during vertical
blanking. The first VBI line is stored beginning at vbi_base,
the second line is stored beginning at vbi_base + vid_pitch,
the third line at vbi_base + (2 x vid_pitch) and on until the
end of the vertical blanking period.
6.9.10.3 Ancillary Data Buffers
Ancillary data packets are stored starting at the buffer
address defined by anc_msg_1. Packet storage continues
to address anc_msg_1 + anc_msg_size at which point the
address is wrapped back around to anc_msg_1. When a
new packet is received, the packet count is incremented.
When software reads a packet from the buffer, it decre-
ments the count by writing a 1 to the Decrement Ancillary
Packet Count bit in the VIP Status register (VIP Memory
Offset 08h[18]).
Ancillary data packets include a checksum. After packet
reception, the internally generated checksum is compared
to the checksum sent with the ancillary packet. If these val-
ues do not compare, the packet is marked bad by writing a
F0 in fill byte immediately following the checksum byte (8/
16 ancillary data) or a 1111 in bits [15:12] of the checksum
DWORD for 10-bit ancillary data. Parity checking is also
performed on the DID, SDID, NN, and checksum WORDs.
Packets with parity errors set the same error bits as when a
checksum error occurs. Parity and checksum errors are
reported in the VIP Status register (VIP Memory Offset
08h). They share a status bit. Parity checking can be dis-
abled via the ANCPEN bit in Control Register 2 (VIP Mem-
ory Offset 04h[26]).
Figure 6-53 on page 479 shows an example of ancillary
packets stored in system memory.
6.9.10.4 Message Passing/Data Streaming Modes
The MSG and STRM modes provide a mechanism for the
AMD Geode CS5536 companion device to send raw data
to the AMD Geode LX processor system memory. MSG
and STRM modes have identical software models. Two
buffers are used (see Figure 6-50). The
VIP_ANC_MSG_1_BASE and VIP_ANC_MSG_2_BASE
registers (VIP Memory Offset 58h and 5Ch) define the two
buffer locations. The VIP_ANC_MSG_SIZE register (VIP
Memory Offset 60h) defines the maximum size of each
buffer. The first packet (data associated with a Start/End
indication) is saved starting at msg_1_base address. The
MB bit in Control Register 1 (VIP Memory Offset 00h[18])
determines when buffer swapping occurs. When MB = 0,
buffers are swapped each packet. When MB = 1, buffers
are only swapped when full. This mode might be used if a
continuous data stream is being delivered. A Message
Buffer Full interrupt occurs when a buffer swap occurs.
Software can read the VIP Status register to determine
which buffer or buffers are full. Software must reset the bit
in order for the buffer to become available. The MSG Buffer
Error status bit (bit 14) is set when a buffer swap occurs
from buffer 1 to buffer 2 with buffer 2 being unavailable or if
a buffer swap occurs from buffer 2 to buffer 1 with buffer 1
being unavailable.
Figure 6-50. Dual Buffer for Message Passing
and Data Streaming Modes
Buffer 1
in use
Buffer 2
in use
buffer1_full/
buffer2_full
Buffer
overrun
buffer2_full
buffer1_full
buffer2_full#
buffer1_full#
mode_2 or mode_3
new PKT
or new PKT