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CDR Tab
11
SNLU159B – April 2014 – Revised September 2018
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Copyright © 2014–2018, Texas Instruments Incorporated
DS125DF1610EVM
12
CDR Tab
Within the ‘Mode Selection’ section there are two options for setting the data rate that the DS125DF1610
expects to receive – ‘Standard Rate’ and ‘Manual Mode.’ ‘Standard rate’ gives the user the option to select
the data rate they are running at for a defined set of protocols, without having to manually program the
expected data rate. See
Table 4
for additional details.
Table 4. Standard Mode Data Rates
Channel Register
0x2F[7:4] Setting
Standard
Data Rates (Gbps)
First Group Divider Settings
Second Group Divider
Settings
0x6
Custom
11.5
1
1
0x7
Interlaken
12.5, 6.25, 3.125
1, 2, 4
1, 2, 4
0x8
CPRI 1
9.8304, 4.9152, 2.4576
1, 2, 4
1, 2, 4
0x9
CPRI 2
6.144, 3.072
2, 4
2, 4
0xA
Infiniband
10, 5, 2.5
1, 2, 4
1, 2, 4
0xB
Ethernet
10.3125, 1.25
8
1
The alternative to ‘Standard Rate’ mode is to program the expected data rate in ‘Manual Mode.’ In manual
mode the desired data rate and corresponding VCO frequency must be entered into Group One or Group
Two. Refer to the datasheet Register Map for setting the 0x2F [7:4] register bits. The bits should be set
based on the expected date rate, taking into account which divider will be required. For example if a data
rate of 1.25 Gbps is entered into the desired VCO frequency for Group One, 0x0C should be selected due
to it having an 8 divider since 1.25 Gbps is a division of 10.3125 Gbps by 8. When a date rate is manually
entered into the ‘Desired VCO Frequency’ field the ‘Write Rate Reg’ push button must be selected to write
it to the register. The desired ppm tolerance is used to adjust the lock range of the CDR for the receiver
channel in question. The VCO count and PPM delta count fields are automatically populated based on the
specified data rate.
Figure 11. CDR Tab