DS125BR800: Optimal setting of MODE and Rx detect setting

Hi,

For 8b10b encoded data at 6.6Gbps

MODE:  Tie Low with 1K to GND

RXDET:  Tie High to VIN if 3.3V is used.  Otherwise tie to VDD.

To start with:

VOD set to 1000mV

DEM set to 0 dB

EQ set to minimum

Then use the Xilinx Rx eye monitor to adjust the EQ and DEM settings for an optimal eye.

Regards,

Lee  

Hi Lee-san

Thank you for your answer.
Please let me know a little more.

・Please tell me specifically what kind of effect will be caused when the MODE pin is set to other than 0 in 8b10b.
・Is the PWDN pin "0"?
・To start with:
What is the reason for setting VOD set to 1000 mV?
・how to set SMBUS and MODE and RX-Detect in the same way.
・When setting with SMBUS, do all registers need to be set except the default setting?
・When setting with SMBUS, is the PIN setting invalid?
・Meaning of 0x08 Block and Allow.
・How to set MODE. Including DEM settings
・Setting method of RXEDT

Regards,

Naoki

Hi Naoki-san,

The Aurora interface uses limiting output drivers and no link training.  The MODE=0 is well suited to this type of signaling - it is very similar to PCIe Gen2 or early versions of SRIO.

The PWDN pin should be set to "0" for normal operation.  When set to "1" the drive is in low power mode.

I like to set VOD = 1000mV to start with because it allows for some DEM if needed on the output side of the device.  As the VOD is reduced, the DEM capability in the DS125BR800 is less effective.

Using SMBus settings there are several registers to write.  The easiest way to start using the SMBus registers is through the Sigcon Architect GUI.  See the link to download the GUI and the "repeater device profile" so you can control the DS125BR800.  www.ti.com/.../SIGCONARCHITECT

Typically with SMBus control we will need to control the following sets of registers.

1. 0x06 = 18'h  //* This enables SMBus control

2. EQ - The default setting is too high.  Most applications have a value of 00'h - 07'h in these registers.

3. DEM - Most applications use DEM = 0dB, but the default setting of -3.5dB may work in your application.

4. VOD - We can set the output amplitude

5. Override Register 0x08 - By default the pin control takes priority.  This register is used to override pin control and allow settings with SMBus

If we leave 0x08 default, then the MODE pin and RXDET pin will continue to control the output MODE and the RX terminations.

Use MODE pin = 0 and RXDET pin = 1

Regards,

Lee

Hi Lee-san

Thank you for your answer.

When you set the same setting as MODE pin = 0, RXDET pin = 1 from SMBUS, please make sure the following is correct?

1. 0x6=18'h // enable SMBus control
2. 0x8=0C'h // [3]Override RXDET= 1: Block RXDET pin control,
                    // [2]Override MODE= 1: Block MODE pin control
3. 0xE=0C'h  //CH0  [3:2]RXDET=11: Input is 50 Ω
4. 0x10=EB'h //CH0  [7]Short Circuit Protection=1: Enable the short circuit protection
                      //CH0  [6]MODE_SEL=1: PCIe Gen-1 or PCIe Gen-2
                      //CH0  [2:0]VOD Control=011: 1.0 V

 CH1-7 has the same settings as 3,4.

Thank you,

Regards,

Naoki