NXP LIN Bus Transceivers Configure Commander/Responder

[TheMDev]

I am looking into purchasing some LIN Bus transceivers such as the NXP TJA1124 or SJA1124 series. However after reading through the data sheet I am a bit confused about configuring the transceiver as a commander or responder.

Referencing Section 3 In this data sheet https://www.nxp.com/docs/en/data-sheet/SJA1124DS.pdf

1. [1]  The SJA1124A LIN commander termination is SPI-configurable and consists of a diode and a pull-up resistor of 900 Ω to 1100 Ω, as specified in LIN 2.x, ISO 17987-4:2016 (12 V LIN) and SAE J2602-1.

2. [2]  The SJA1124B LIN commander termination is fixed and consists of a diode and a pull-up resistor of 900 Ω to 1010 Ω.

Does this mean that it can be configured via SPI for SJA1124A but not SJA1124B?

Or that SJA1124A can be commander or responder but SJA1124B can only be a commander? 

So is this chip configurable as a commander/responder if so is the termination internal or do extra components need to be added to the board?

[christoph_bierwipfl]

Hi, for me it is not clear if SJA1124A/SJA1124B is able to works as a responder?

[guoweisun]

Please read datasheet page 15 for more detail explain--

The SJA1124A contains Multiple Time Programmable (MTP) non-volatile memory (NVM)
cells that allow the default configuration of the LIN commander pull-up to be programmed
(the NVM registers are read-only in the SJA1124B).

[TheMDev]

Hi, thank you for your response and clarifying the difference between the SJA1124A/SJA1124B. However, referencing Table 1 and Table 12, I am still unclear if the SJA1124A can be configured as a commander and responder. The note under table one lists that the pull-up resistor is approximately 1k. Referencing table 12, it only allows the configuration of the 1k resistor for different power states. However, to my knowledge, responder nodes are typically terminated with a 30k pull-up. So can the SJA1124A be configured as a responder with an external 30k pull-up, or is it only able to be a commander?

[guoweisun]

Hi :

The LINx pins of the xJA1124 are equal. A LIN slave pull-up Rslave and LIN master pull-up
Rmaster, each in series with a reverse current protection diode, are internally connected to
pin BAT. The LIN master pull-up Rmaster can be disabled in case of detected faults, e.g.
short-circuit between LIN and ground. In the SJA1124A, the LIN master pull-up
termination can be programmed per channel via the MCFG register (refer to section
“Programming of MTPNVM” in the data sheet [1]. Note: The number of programming
cycles should not exceed 63 (3Fh). This could lead to malfunction of the device.

The specified range of Rmaster [1][2] for the variants SJA1124A, TJA1124A and TJA1124B
differs from the variants SJA1124B and TJA1124C. As illustrated in Fig 3, latter variants,SJA1124B and TJA1124C, have a lower maximum value whereas the minimum value is
unchanged.

With this lower Rmaster maximum value, the maximum RC time constant of the LIN
network can be reduced. This enables the use of an integrated LIN master pull-up in LIN
networks, which are designed based on an external LIN master pull-up with 1 kΩ ±1%.

[nxf33425]

I am still confused with whether SJA1124 can be used as a slave or not.

We tried by programming MCFG bits to 00(i.e. terminated with Responder), but still not able to receive data which master is sending

[Rikus]

Changing the pullup fuse:
reg 0x10 = 0x80 to disable sleeping
reg 0xf0-f2 reads 0xAA 0x40 0x00
0xf0 = 0
0xf2 = 0xA1
Wait at least 1 second after setting the crc