ADIN1111CCPZ-R7 datasheet(25/109 Pages) AD

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Data Sheet

ADIN1111

ON-CHIP DIAGNOSTICS

analog.com

Rev. A | 25 of 109

design, product testing, as well as at installation in the system, and

during the lifetime of the system.

Signal-to-Noise Ratio and Bit Error Rate

There is a statistical relation between a communication channel

SNR and bit error rate (BER). The relation between white noise

SNR and 10BASE-T1L BER is shown in Figure 16.

Figure 16. Statistical Relation Between SNR and BER in 10BASE-T1L

The IEEE 802.3cg-2019 standard requires the 10BASE-T1L BER

≤ 10−9, in the presence of the relevant noise. For context, the

BER 10−9 means 1 bit error every 100 sec in continuous 10 Mbps

data, which translates to approximately an SNR of 20.0 dB on the

10BASE-T1L PHY as shown in Figure 16.

With an SNR of 21.0 dB, the BER must be 10−11, which is 1 bit error

every 10,000 sec or 2¾ hour, and with an SNR of 22.0 dB, the BER

must be 10−14, which is 1 bit error in 115 days. These examples

illustrate how the SNR relates to the reliability of the 10BASE-T1L

Ethernet.

There are always some errors in any data communication channel.

The communication protocols, implemented and operating above

the Ethernet physical layer, such as TCP/IP in general use cases,

or the specific protocols for industrial or building automation ensure

data integrity by frame repetition or error correction as appropriate

for a given application. However, the link quality and related error

rate of the physical layer must be kept at a certain level for reliable

connection. The acceptable error rate may be different in noncritical

monitoring compared to a time critical automation network or safety

application.

Mean Squared Error at PHY Slicer

The link quality monitoring inside the PHY is implemented as an

MSE measurement.

The 10BASE-T1L Ethernet uses PAM3 modulation—the data sent

over the cable is coded into symbols of three voltage levels.

Inside the receiver, after analog and digital signal processing, is

a device called a slicer, which makes the decisions whether the

incoming signal voltage level represents a +1, 0, or –1 symbol. An

ideal received and scaled signal is already at these exact levels.

However, the noise coupled to the Ethernet channel from various

sources affects the real signal.

The PHY measures, for each received symbol, an error between

the output of the slicer and the received signal already scaled to the

correct amplitude level as shown in Figure 17. The mean square

value of these errors is then calculated and reported in the PHY

MSE_VAL register.

There is a direct relation between the MSE and SNR.

SNR= 1MSE

(1)

SNRdB =−MSEdB

(2)

Figure 17. Error Between Ethernet PHY Slicer Input and Output

MSE Reading

The ADIN1100, ADIN1101, ADIN1110, ADIN1111, and ADIN2111

automatically measure the MSE in the background when the

10BASE-T1L link is active and makes it available in the MSE_VAL

The MSE_VAL register can be read via the management interface

(MDIO or SPI) anytime. After power-up or reset, before the first link

is up, the MSE_VAL register value is zero. When the 10BASE-T1L

link is up, the MSE_VAL register is updated after each received

symbol (every 133 ns). When the link drops, the register still

updates. However, the MSE value is incorrect. Therefore, reading

and processing the MSE is logical only when the 10BASE-T1L link

is up.

The frequency of reading the MSE_VAL register is not limited,

and it can be read as often as the management interface allows.

Therefore, how often MSE_VAL must be read depends on how fast

the link quality is expected to be changing and on how often the link

quality needs to be assessed and reported or recorded in the end

system application.

An example of polling the link status and reading the MSE is as

follows:

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