PNX1301 PHILIPS [NXP Semiconductors], PNX1301 Datasheet - Page 135

• Manufacturer Part Number: PNX1301
• Description: Media Processors
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
It is recommended that EVO be stopped (by negating
VO_CTL. ENABLE) before block level power down is
started, or that SLEEPLESS mode is used when global
power down is activated.
7.19
The PLL filter reduces the phase jitter of the DDS synthe-
sizer output. It can also be used to multiply the DDS out-
put frequency by 2 . The DDS and PLL filter together
provide a high-quality, accurately-programmable output
video clock. The PLL filter block is shown in
At hardware reset, the output multiplexer is set to 0x3,
and the PLL system is disabled. To start the PLL system,
the following steps must be performed:
1. Assign a DDS frequency. This starts the DDS. Allow
2. Choose a value for PLL_S and PLL_T. For 8-40 MHz
3. Choose a value for CLOCK_SELECT. For 8-81 MHz
Table 7-12. DDS and PLL example settings
Figure 7-32. PLL filter block diagram.
4 – 10 MHz
8 – 45 MHz
40 – 81 MHz
9
Frequency
for at least 31 DSPCPU cycles for the DDS frequency
setting to take effect.
operation, a value of 1 (which selects division by 2) is
recommended.
operation, CLOCK_SELECT = 00 is recommended.
Desired
CPU Clock
3
Square-Wave DDS
DDS AND PLL FILTER DETAILS
FREQUENCY
8 – 20 MHz
8 – 45 MHz
20 – 40. 5 MHz
DDS frequency
0
div S+1
PLL_S
1 (divide by 2)
1 (divide by 2)
1 (divide by 2)
PLL_S
Figure
Detect
Phase
1 (divide by 2)
1 (divide by 2)
3 (divide by 4)
7-32.
PLL_T
4. Assign values to the VO_CTL register containing the
Once the PLL is locked, small changes to the DDS fre-
quency are allowed, and the VO_CLK output will
smoothly track the frequency change.
Note: Most consumer electronics equipment imposes
very high precision requirements on the value of the col-
or burst frequency . A video encoder will derive the color
burst frequency from VO_CLK. When changing the
VO_CLK frequency in software to phase-lock the EVO to
a master reference, special care is required to keep the
color burst signal frequency within a tolerance of about
50 ppm. When using a Philips DENC (Digital Encoder),
the color burst frequency is derived from the master
DENC frequency by a programmable synthesizer on the
DENC chip. In this case, VO_CLK changes larger than
50 ppm are allowed by changing the DENC synthesizer
over its I
change.
Table 7-12
PRELIMINARY SPECIFICATION
div T+1
Loop
Filter
PLL_T
above choices. The first assignment with
CLOCK_SELECT not equal to 0x3 enables the PLL
system. Allow for a maximum of 50 microseconds to
achieve lock.
01 (T divider)
00 (VCO)
00 (VCO)
CLOCK_SELECT
2
C interface to compensate for the VO_CLK
illustrates recommended settings.
8–90 MHz
VCO
Custom low speed video
Standard or 16:9 digital video
High pixel rate custom video
CLOCK_SELECT
00
01
10
11
CLKOUT
Enhanced Video Out
Usage
(to Frame Timing Gen.)
VO_CLK Internal
VO_CLK
7-25