Table of Contents
Advertisement
www.ti.com
4.2.9
Lock Data Rate Indication
There could be a need to realize the data rate the device has locked to. In this case, register 0x02[4] is
read to make sure the device is locked. Then VCO divisor setting indicates the data rate.
RAW FF
04
RAW 0C
00
RAW 02
18
RAW 0C
30
RAR
02
38
RAW 0C
00
4.2.10
Read Horizontal and Vertical Eye Opening
The LMH0318 produces two readings to indicate line signal quality: The Horizontal Eye Opening (HEO)
and the Vertical Eye Opening (VEO) are indications of signal quality. These parameters can be read by
the host processor or the LMH0318 can be optioned to cause interrupt if HEO/VEO reach a threshold.
To convert the HEO reading to Unit Interval (UI) eye opening, we need to divide the HEO reading, in
decimal, to 64.
HEO = (Decimal Reg0x27)/64
For example, if the HEO reading is 0x31 (49 decimal) then the HEO UI eye opening would be
49/64=0.77UI. This means the HEO is about 77% open.
Similarly, VEO has 64 steps as well. The chip automatically covers differential peak to peak value from +/-
100mV to +/-400mV and reports the value adjusted to +/-100 mV. Thus, each step is 200/64 or 3.125 mV.
Therefore VEO in mV = (Decimal VEO value)×3.125. For example, if we read 0xC8 (200 decimal) for the
VEO reading, this corresponds to 200 × 3.125 mV = 625 mV vertical eye opening.
RAW FF
04
RAW 11
00
RAW 3E
80
RAR
27
xx
RAR
28
xx
RAW 3E
00
RAW 11
20
SNLU183 – September 2015
Submit Documentation Feedback
07
//Select Channel Registers
F0
//Setup register 0x0c to read lock indication bit 4
18
//Wait until bit 4 is set indicating device is locked
F0
//Setup register 0x0C to read the VCO divider setting
38
//Read divider settings
// 02[5-3] = 010'b 2.97 Gbps
// 02[5-3] = 011'b 1.485 Gbps
// 02[5-3] = 100'b 270Mbps
F0
//Setup the default value for Reg 0x0C
07
//Select Channel Registers
20
//Enable EOM
80
//Enable HEO/VEO
FF
//Read HEO, convert hex to dec, then divide by 64 for value in UI
FF
//Read VEO, convert hex to decimal and Multiply by 3.125mV
80
//Restore initialization setting
20
//Power down EOM
Copyright © 2015, Texas Instruments Incorporated
Device Configuration
LMH0318 Programming Guide
13
Advertisement
Table of Contents
