【NXP PJF7992】A brief introduction to the two working modes (SPI mode and single-wire mode)

1. Overview

 
             The serial interface of PJF7992 can be configured as SPI or single-wire mode. The two working modes are applicable to different scenarios: SPI mode is suitable for base stations with embedded structures, and it can quickly and directly access base stations with embedded structures; while single-wire mode is more suitable for remote base stations, which only requires three interconnection wires ( VBAT , GND and LIN ) and has a good signal-to-noise ratio in serial data communication. The following article will briefly introduce the configuration and basic characteristics of the two working modes.

 
2. Configuration of two working modes
        
       The working mode of PJF7992 is determined by the high and low levels of pin IOREF:

 

Note: 1. In SPI mode, the interface signals (DI, DO, CLK) are oversampled to improve EMI robustness. The SPI signals are sampled every 125ns .
2. Single-wire mode uses the on-chip LIN transceiver to communicate with the device remotely. No external microcontroller is required, and the LIN transceiver is controlled by an internal state machine. The CSN, DI, and CLK pins have no function and can be grounded.

 
3. SPI Mode

 
3.1 SPI Mode Timer
           The protocol layer of the SPI first interface operates MSB . The input (DI) data is locked on the rising edge of the clock line, while the output (DO) data is provided on the falling edge of the clock line, as shown in the following figure:

                        

3.2 SPI Command Byte

The command byte consists of a 6 -bit command code and a 2 -bit parity check to increase data integrity.
                     
                     

3.3 SPI Data Byte

The data bytes can consist of anything, depending on the application
                    
                      

4. Single-line mode

 
4.1 Single-wire mode timer

The protocol layer of the single-wire interface operates LSB first . If the device and the interface are in the powered-down state, the communication always starts with a remote wake-up, followed by a synchronization sequence and a protected identifier (PID) . After this sequence, the interface waits for the first command. To wake up the device, the LIN (dominant) for a certain time line must be forced to 0 . After the device initiates TWUP , the interface waits for the synchronization sequence.
                        
                        
Figure 4.1.1 Single-wire: Standard communication sequence
                         
Figure 4.1.2 Single-wire communication sequence without new synchronization sequence

           
4.2 Single-wire mode command byte

The command byte consists of a 6 -bit command code and a 2 -bit parity check to increase data integrity.
                              
                                    
   

4.3 Single-wire mode data byte

The data bytes can consist of anything, depending on the application
                                   
                                     

 V. References

            【1】 f7992A_2015