How to use SEL1/READ_EN# on DS125MB203

Hi Neil,

The DS125MB203 EEPROM configuration is limited by any requirements to configure the SEL0/1 logic.  The best method to control DS125MB203 SEL1 logic when using an EEPROM load is by writing the registers directly after the initial configuration is complete.

Regards,

Lee

Given that offsets 0x5E and 0x5F are not settable through the EEPROM - what will the state of the channels controlled by SEL1 be after READ_EN# is asserted low - will it behave as though SEL1 is low? Would I only need to write to the device to override SEL1 pin if I need to connect the A side signals?

Hi Neil,

The SEL1 control should behave as though the input is floating, as the SEL1 net is replaced by the READ_EN# function when Master Mode is set by leaving EN_SMB = F.

Yes, you would only need to override the SEL1 pin if you are configuring settings for Lane 1. The A side signals can correspond to either Lane 0 or Lane 1, so if you only need to connect the A side signals for Lane 0, you will not need to implement the SEL1 pin override.

Thanks,

Michael 

Just to confirm the SEL1 functionality in Master Mode is as if the SEL1 pin is floated? i.e. Not 0,1 or pulldown.

And therefore, the S_INA1+/- pins are connected to D_OUT1+/- and D_IN1+/- is connected to S_OUTB1+/- (we intend to tie INPUT_EN to 0).

Thanks

Hi Neil,

Yes, this is my expectation. Please allow me a day or two to confirm with our designers.

Regards,

Michael

Hi Neil,

After checking with our designers, it appears that I have mistyped.

When operating in SMBus Master Mode, the state of the SEL1 pin is ignored and registers take precedence. Since the default state of SEL1 Control in Reg 0x5F is 00'b, I expect that the select control for SEL1 defaults to 0 in Master Mode. (S_INB1+/- to D_OUT1+/- and D_IN1+/- to S_OUTB1+/-).

Thanks,

Michael