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.

guoweisun_0-1676359749156.png

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