Page 41 - USI Newsletter No.94
P. 41

Intelligence  資訊特快車
 Express                                                                                                   NO.94


 The Introduction of I3C  High Data Rate Transmission             In contrast with I2C transfer rate, I3C in SDR mode is

               The I3C provides the user with various communication
 Episode 2     modes. SDR (Single Data Rate) is a default mode    about 11 times faster than I2C. In HDR-TSP mode, I3C

               compatible with the exchange of messages of the
                                                                  can even be up to about 33 times faster speed than
               legacy I2C interface. HDR (High Data Rate) includes   I2C. The following figure, Fig 3 shows the transfer
               several message exchange modes that are not        time comparison based on effective 1KB data. In
 Author: Shanghai Zhangjiang Site / MCS / SAI / Homer Liu
               compatible with I2C. HDR has HDR-DDR, HDR-TSP,     addition, I3C is using single lane to transfer data in
               HRD-TSL and HDR-BT. The typical data rate of I3C is   the following comparison.
 n the previous issue, we introduced some advantages and the basic framework structure of I3C. Now,
               10Mbps. But the data rate will be up to 30Mbps in HDR
 let�s take a look at some features of I3C. In practical design and development, these characteristics of I3C   with single lane. If the HDR enables four lanes, the
 I can provide us with more design ideas and insights.  data rate can be up to 100Mbps. The following picture,
               Fig 2 is an illustration of data rates.
 Now let's dive into some of its cool features.
 Two Signal Lines


 Two signals, SDA and SCL are adopted. SDA supports both open-drain and push-pull mode. SCL supports push-
 pull (avoid power absorption and slow rise-time like I2C), does not support the ability of slaves to stretch the
 clock. Push-pull mode achieves I3C high data rate.

 In-Band Interrupt


 Slave can spontaneously initiate an interrupt. The in-band function allows I3C slave to initiate a START   Fig 2 Multi-lanes Data Rate  Fig 3 1KB Data Transfer Rate Comparison
 transaction whenever they deem it necessary, so as to send its address to master. If more than one slave tries to   Hot-Join
 access the bus simultaneously, an arbitration will be triggered by the means of the higher priority, the lower   Thanks to hot-join feature, the following scenarios can be easily realized.
 address. No extra interrupt GPIO is required during the procedure.   •  Inactive device on the bus returns active
               •  Physically inserted device after I3C bus has already been configured
 In-Band Reset  These target devices can use the reserved address, 7'h02 to initiate the in-band interrupt, so as to complete the

 Unlike I2C, I3C does not need an extra reset IO to achieve the bus reset. I3C can realize the bus reset by using   hot-join.
 command code RSTACT. Master can reset one or more selected targets and avoid resetting any others. Abundant
 reset levels can achieve different resets ranging from resetting only the I3C peripheral to resetting the whole   Excellent Power Consumption
 target device.  Although data rate is enhanced, I3C interface is more energy-efficient than I2C, even in the compatible I2C mode.
               Figure 4 shows the amount of Energy (mJ) consumed for an effective single lane of 1kB data. In contrast with I2C,
               I3C SDR mode can save 4.3 times energy, I3C HDR-TSP mode save up to 18 times.
















 Fig 1 I3C Reset Pattern



                                                 Fig 4 I3C vs. I2C Energy per 1KB Effective Data

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