TJA11100 pin strapping issue

[waynekuo]

Hi Expers,

I'm new on TJA1100, and I have question on pin strapping.

As datasheet description on section 6.11, TJA1100 will detect CONFIG0, CONFIG1, CONFIG2, CONFIG3, PHYAD0, and PHYAD1 while power-on or H/W reset to configure operation mode and PHY address.
These pins are also use for RXD2, RXD3, RXER, RXDV, RXD0, and RXD1 on MII mode.

As TR1329 EVM board reference design, these pins are connect to MCU/MPU MII interface and also connect to JP16 ~ JP20 to set pull-up/upll-down.

My question is:
1. Are these pull-up/pull-down designs necessary?
2. If not, dose TJA1100 have default operation mode and PHY address? What are the default setting?

Best Regards,
Wayne Kuo

[martin_kovar]

Hello,

from my point of view, it is not necessary to connect pull-up/pull-down resistors, but please pay attention to this section:

Additionally, it must be ensured that the bits, configured by pin strapping, are not overruled by the microcontroller pin configuration during initialization. This can easily be achieved, if  
-  The according microcontroller pins are high-ohmic during initialization phase (recommended),
-  The relevant pins are configured as specified by pin strapping or  
-  The RST_N pin is not released until the relevant microcontroller pins are configured (high-ohmic).

You must ensure, there is required logic value on pin during device startup. This can be done via external resistors, or via microcontroller pins.

For the features configured by pin strapping, there are not any default values. These default values are determined by logic level on pin during device startup.

Regards,

Martin