Analog Devices ADV8005, Hardware Reference Manual

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UG-707 ADV8005 Hardware Reference Manual
6.11.4.2. CTS Parameter
The CTS value is an integer number that satisfies Equation 26 .
s
CLK TMDS
Average
f
N f
CTS
128
_
=
Equation 26: Relationship Between N and CTS
6.11.4.3. Recommended N and Expected CTS Values
The recommended values of N for several standard pixel clocks are given in Table 61 to Table 63 .
The
ADV8005 has two modes for CTS generation.
Manual mode: Manual mode is selected by setting cts_sel to 1. In manual mode, the user can program the CTS number directly into the chip
via the cts_manual[19:0] field. Manual mode is good for coherent audio and video, where the audio and video clocks are generated from the
same crystal; thus CTS should be a fixed number.
Automatic mode: Automatic mode is selected by setting cts_sel to 0. In automatic mode, the chip computes the CTS based on the actual audio
and video rates. The result can be read from the cts_internal[19:0] field. Automatic mode is good for incoherent audio or video, where there is
no simple integer ratio between the audio and video clock.
The 20-bit n value used by the Tx core of the
ADV8005 can be programmed in the n[19:0] field.
cts_sel , TX2 Main Map, Address 0xF40A[7]
This bit is used to specify whether CTS is automatically or manually set.
Function
cts_sel Description
0 (default) Automatic CTS. Use the internally generated CTS value
1 Manual CTS. Use the CTS programmed via CTS_MANUAL[19:0]
cts_manual[19:0]
, TX2 Main Map, Address 0xF407[3:0]; Address 0xF408[7:0]; Address 0xF409[7:0]
This signal is used to manually set the Cycle Time Stamp (CTS). This parameter is used with the N parameter to regenerate the audio clock
in the receiver.
cts_internal[19:0]
, TX2 Main Map, Address 0xF404[3:0]; Address 0xF405[7:0]; Address 0xF406[7:0] (Read Only)
This signal is used to readback the automatically generated Cycle Time Stamp (CTS) parameter. This parameter is used with the N
parameter to regenerate the audio clock in the receiver.
n[19:0] , TX2 Main Map, Address 0xF401[3:0]; Address 0xF402[7:0]; Address 0xF403[7:0]
This signal is used to specifies the audio clock regeneration parameter N. This parameter is used with CTS to regenerate the audio clock in
the receiver.
Table 61: Recommended N and Expected CTS Values for 32 kHz Audio
32 kHz
Pixel Clock (MHz) N CTS
25.2/1.001 4576 28125
25.2 4096 25200
27 4096 27000
27 * 1.001 4096 27027
54 4096 54000
54 * 1.001 4096 54054
74.25/1.001 11648 210937 – 210938
74.25 4096 74250
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