TDA4VMXEVM: 25MHz Clock output

Hi Alex

MCU_CLKOUT0: MCU domain CPSW2G

TRM Reference: Figure 12-485. MCU_CPSW0 Integration

The MCU_CPSW0 module integrated in the device supports internal and external clock sources in RMII
mode. Figure 12-482 shows the internal clock source for RMII_MHZ_50_CLK clock. It is 50 MHz clock
source that is provided on the MCU_CLKOUT0 device pin. This clock has to be routed on the PCB to the
MCU_RMII1_REF_CLK device pin and the external PHY, RMII clock input.

Can be set to 25 MHz using CTRLMMR_MCU_CLKOUT0_CTRL register - TRM reference 5.1.2.4.66 CTRLMMR_MCU_CLKOUT0_CTRL Register

CLKOUT: Main Domain CPSW9G

TRM Reference: Figure 12-886. CPSW0 Integration
Can be set to 25 MHz using TRM reference 5.1.3.4.168 CTRLMMR_CLKOUT_CTRL Register

For this question:

3. Could CLKOUT and MCU_CLKOUT0 be used to as 2 Ethernet PHY clock input source?

I am trying to understand your usecase, Do you intend to source the clock from CLKOUT or MCU_CLKOUT0 to more than 2 Ethernet PHYs?

Thanks and Regards

Piyali

Dear Piyali.

we have 2 pcs RGMII PHY on the board, let me named them A and B.

I would like to connect CLKOUT to A PHY, and connect MCU_CLKOUT0 to B PHY, is it possible?

if yes, have any point need to concern for such design?

by the way, have other pin also output 25MHz clock if CSI Deserializer also need this?

Hi Alex,

For the 2 RGMII you could drive 2 different PHYs with the 2 clock outputs.

For the CSI, I will loop in our HW experts to comment further.

Thanks and Regards

Piyali

Alex,

What is the specifications of the input clock your deserializer is expecting?  That will help us narrow down on the choices.  Alternatively, have you considered DS90UB926?  This deserializer offers users the opportunity to extract clock from the high speed serial stream.  A sample overview of the part is quoted below; more details can be found in the device datasheet.

" The DS90UB926Q-Q1 deserializer attains lock to a data stream without the use of a separate reference clock source, which greatly simplifies system complexity and overall cost. The deserializer also synchronizes to the serializer regardless of the data pattern, delivering true automatic plug and lock performance. It can lock to the incoming serial stream without the need of special training patterns or sync characters. The deserializer recovers the clock and data by extracting the embedded clock information, validating then deserializing the incoming data stream. "

Have a great day!

Best,

Shiou Mei

Dear Shiou Mei

I have a question about CSI portion(Camera). when I connect DS90UB954 to TDA4M

should I choose 2x CSI (2 lane) or 1x CSI( 4 lane), their differnce is as below

One: CSI0_RXCLK(P/N), CSI0_RX0(P/N),, CSI0_RX1(P/N), CSI1_RXCLK(P/N), CSI1_RX0(P/N),, CSI1_RX1(P/N) are used

Or

The other: CSI0_RXCLK(P/N), CSI0_RX0(P/N), CSI0_RX1(P/N), CSI0_RX2(P/N), CSI0_RX3(P/N) are used

Alex,

How does your application look like?  How many cameras do you expect to connect and what is the bandwidth the system will require? 

The # of lanes to use will depend on the bandwidth your system requires.  Each CSI2 lane is rated for 2.5 Gbps (wire rate) support, that means a 2-lane configuration will support up to 5 Gbps and a 4-lane configuration will support up to 10 Gbps.  If 2-lane configuration can cover your needs, then that may be preferred to save on pin counts.

Have a great day!

Best,

Shiou Mei

Dear Shiou Mei.

So, my understanding is if we want to use 2 pcs Camera connect into DS90UB954, this action causes pin Rin0PN/Rin1PN will be used, so CSI_CLK0PN/CSI_CLK1PN is used as well, 

if our application is connect 2 camera with througput over 5 Gbps each, that DS90UB954 should not be suitable, am I right?

Alex,

Looks like our highest deserializer FPD-Link-III line rate is rated for 4.16 Gbps (UB960).  I will check with our FPD-Link team to understand if we have any that will support 5 Gbps per lane.  Please help provide details of the serializer (brand, model#) you plan to use in your application that will output at 5 Gbps line rate.

Best,

Shiou Mei