SNLA386 May   2021 DS250DF810 , DS280DF810

 

  1.   Trademarks
  2. 1Introduction
  3. 2Reading Junction Temperature Procedure
  4. 3Extending Temperature Lock Range (TLR) Procedure
  5. 4Summary

2 Reading Junction Temperature Procedure

Table 2-1 provides a programming procedure to read the junction temperature from the DS2X0DF810 25-28G retimers. This procedure is beneficial for occasional debug and link monitoring.

Note: The accuracy of the on-die temperature sensor is not ensured by production testing. Through empirical observation, the temperature sensor readback exhibits a typical TJ accuracy of approximately ±7°C. Therefore, the procedure should be restricted to occasional debug use only.
Table 2-1 Programming Procedure for Reading Junction Temperature
STEP REGISTER SET OPERATION

REGISTER ADDRESS

[HEX]

REGISTER VALUE

[HEX]

WRITE MASK

[HEX]

COMMENT
Normal Retimer configuration
Perform all steps to configure the Retimer as normal. Junction temperature measurements are the most useful when the device is operating in a configuration which mimics the mission-mode configuration.
Configure Retimer for temperature readback
1 Shared Write FF 10 FF Select Channel 0 – Channel 3 shared registers
2 Shared Write 04 40 40 Reset Channel 0 – Channel 3 shared registers
3 Shared Write FF 20 FF Select Channel 4 – Channel 7 shared registers
4 Shared Write 04 40 40 Reset Channel 4 – Channel 7 shared registers
5 Shared Write FF 10 FF Select Channel 0 – Channel 3 shared registers
6 Shared Write 0F 00 FF Enable temperature detection CH0-CH3
7 Shared Write FF 20 FF Select Channel 4 – Channel 7 shared registers
8 Shared Write 0F 00 FF Enable temperature detection CH4-CH7
9 Shared Write FF 01 FF Disable broadcast write to all channels, read from channel selected in Shared Reg_0xFC
10 Shared Write FC 04 0F Select single channel
11 Channel Write 19 01 C1 Enable channel temperature detection
12 Channel Write 18 01 03 Enable channel temperature detection
13 Shared Write FF 10 FF Select Channel 0 – Channel 3 shared registers
14 Shared Write 0C 00 38 Configure the input to the analog-to-digital converter (ADC)
15 Shared Write 0C 02 03 Enable ADC
16 Shared Write 0C 04 04 Reset ADC
17 Shared Write 0C 00 04 Set ADC to capture Analog Voltage
18 Wait 200 µs
19 Shared Write 0C 00 02 Disable ADC to freeze value
Temperature readback
20 Shared Read 0D -- -- DSAR[7:0] = Reg_0x0E[7:0]
21 Shared Read 0E -- -- DSAR[9:8] = Reg_0x0E[1:0]
  • Decimal_representation_of_temperature_code = (Reg_0x0E and 0x03) × 256 + Reg_0x0D
  • TJ = (0.73 × Decimal_representation_of_temperature_code) – 340, in degrees C
  • Note: The numbers 256 and 340 in the previous equations are decimal numbers.
22 Shared Write FF 10 FF Select Channel 0 – Channel 3 shared registers
23 Shared Write 04 40 40 Reset Channel 0 – Channel 3 shared registers
24 Shared Write FF 20 FF Select Channel 4 – Channel 7 shared registers
25 Shared Write 04 40 40 Reset Channel 4 – Channel 7 shared registers
26 Shared Write FF 01 FF Enable read/write from/to channel selected in Reg_0xFC
27 Shared Write FC 04 0F Select single channel
28 Channel Write 19 00 C1 Disable channel temperature detection
29 Channel Write 18 00 03 Disable channel temperature detection