pnx1700 NXP Semiconductors, pnx1700 Datasheet - Page 660

• Manufacturer Part Number: pnx1700
• Description: Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
Table 4: VLD Commands
PNX17XX_SER_1
Preliminary data sheet
Code Command
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
Shift the bitstream
by ‘‘count’’ bits
Parse for a given
number of
macroblocks
Search for the next
start code
Reset the Variable
Length Decoder
Initialize the VLD
Search for the
given start code
Parse one row of
macroblocks
Flush Write FIFOs Command Done
Parse Long
Flags Set
(after completion
of the command) Description
Command Done
Command Done
and/or Start Code
Detected
Start Code
Detected and
Command Done
Command Done
None
Start Code
Detected and
Command Done
Start Code
Detected
Command Done
The CPU must wait for the VLD to halt before the next command can be issued. Note
that there are several ways in which a command may complete. Only a successful
completion is indicated by the command done bit in the status register. A command
may complete unsuccessfully if a start code or an error is encountered before the
VLD shifts the number of bits in its internal shift register. The shift register
value is available in the VLD_SR register.
The flag is reset by issuing the new command.
VLD parses for a given number of macroblocks; however, if VLD
encounters a start code, the parsing action will be terminated and VLD sets
only the start code detected flag. If VLD parses the given number of
macroblocks without encountering a start code, VLD will set the command
done flag.
The start code detected flag is reset by writing a ‘1’ value to the flag.
The command done flag is reset by issuing the new command
VLD search for a start code. The search code has 0x000001 prefix and
additional 8-bit value; a 32-bit value with 0x000001 prefix.
the start code detected flag is reset by writing a ‘1’ value to the flag.
The command done flag is reset by issuing the new command
Refer to
The bit count register is initialized to zero. The initialization action is
immediate without any delay.
VLD search for a start code with a given 8-bit lsb of the 32-bit start code.
The search code has 0x000001 prefix and the additional 8-bit value is
given in the ‘count’ field of the VLD_COMMAND register.
The start code detected flag is reset by writing a ‘1’ value to the flag.
The command done flag is reset by issuing the new command
This command instructs the VLD to parse one complete row of
macroblocks. If the row contains more than one slice, VLD parses the
intermediate slice headers without CPU intervention, provided these slice
headers have a 0 bit after the 5-bit quantizer_scale_code. If the VLD
encounters a start code different from the start code of the current slice, or
if the slice header has a 1 bit after the quantizer_scale_code, it sets the
Start-Code-Detected flag and ends the operation.
WARNING: The ‘Count’ field of the VLD_COMMAND register is still in
effect as in the ‘Parse A Number Of Macroblocks’ Command: VLD stops
and sets the Command-Done flag after ‘Count’ macroblock headers are
parsed. ‘Count’ must be set to at least mb_width (number of macroblocks
per row in the picture) to guarantee the entire row is parsed before the VLD
stops.
The VLD flushed the remaining macroblock header data and the remaining
run-level data to the main memory.
This command instructs the VLD to parse and to continue as long as the
next start code ID is for the next slice. Any other start code ID will cause
the VLD to stop and interrupt with the ‘Command Done’ status bit set.
Note the count field cannot be programmed to 0.
Rev. 1 — 17 March 2006
Chapter 21: MPEG-1 and MPEG-2 Variable Length Decoder
Section 3.4 Error
Handling.
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX17xx Series
21-8