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Device Configuration
4.2.4
Selective Data Rate Lock
In default mode, the LMH0318 is configured to automatically lock to all SMPTE data rates. The LMH0318
can be configured to lock to certain data rate or restricts the dividers so the CDR can only lock to the
desired data rate. This enables faster lock time.
Table 3. SMPTE Data Rate Selection
REGISTER
FUNCTION
1: Enable CDR Lock to 270Mbps
Reg 0xA0[4]
0: Disable CDR Lock to 270Mbps
1: Enable CDR Lock to 1.485/1.4835 Gbps
Reg 0xA0[3]
0: Disable CDR Lock to 1.485/1.4835 Gbps
1: Enable CDR Lock to 2.97/2.967 Gbps
Reg 0xA0[2]
0: Disable CDR Lock to 2.97/2.967 Gbps
For example, to enable lock to 3G, HD, and 270 Mbps, the following script can be used:
RAW
FF
04
07
//Select Channel Registers
RAW
A0
1C
1F
//Enable Lock to ST 424, ST 292, and ST 259 only
RAW
0A
0C
0C
//Initialize CDR State Machine Control
RAW
0A
00
0C
//Release CDR Reset
Alternatively, the following sequence can be used to disable lock to certain data rates (for example 3G):
RAW
FF
04
07
//Select Channel Registers
RAW
A0
00
04
//Disable Lock to 3G
RAW
0A
0C
0C
//Reset CDR
RAW
0A
00
0C
//Release CDR Reset
4.2.5
Check Status of LOS (Loss Of Signal) on Input 1 or Input 0
The LMH0318 has two inputs and each input has its own signal detector. Based on signal detect status
and input channel selected, the device automatically goes into power down. For example, if IN0 is
selected and there is no signal on IN0 then the device, CDR and output drivers go into power down. The
following macro checks the status of the signal detects on IN0 or IN1:
RAW
FF
04
07
//Select Channel Registers
RAW
1
01
01
//Read LOS of IN0
RAW
1
02
02
//Read LOS of IN1
9
SNLU183 – September 2015
LMH0318 Programming Guide
Copyright © 2015, Texas Instruments Incorporated