SC18IM700 vs SC18IM704 UART-to-I2C bridge questions...

[wmwiese]

Hello team...
Several questions on SC18IM700 vs SC18IM704 UART-to-I2C bridge devices.

1. Which one is the latest product - is either one "Not recommended for new designs"??
    [The 704 has a later doc rev date but that may not indicate which chip is latest]

2.  Appears major difference btwn '700 vs '704 devices is pinout arrangement. Yet from viewing questions in this forum there may be other differences   (for example  it appears there's a ' V ' version info string command on the '704 device but perhaps not on the '700, and the 704 has difference in input port configurations).
 
So besides pinout, what other key differences exist btwn the '700 and '704 - speed, reliability, extra commands?  Is there any recommendation for special cases to use one IC vs the other?

3.  Writing to {BRG0, BRG1} register pair sets UART baudrate.  What is max baudrate I can set such that 18IM7xx works reliably?  

[It appears that {BRG1,BRG0}= $0000 setting maxes out at 460.8K bps - valid/reliable setting?
 With {BRG1,BRG0} = $0010 setting, UART should supposedly at 230.4Kbps - valid/reliable??
 Is one IC version better at higher speed serial comms than the other??]


4.   I2C clock rate is configurable via I2C_CLKL, I2C_CLKH registers (registers $07, $08).
But it appears they are calculated differently & have different defaults.

For '700 bridge IC doc I see default settings of I2C clock regs { R07, R08 } ==  {$13, $13}.
For '704 bridge IC doc I see default settings of I2C clock regs { R07, R08 } ==  ($13, $00}.

The settings are kinda (awkwardly?) expressed in the '700 doc - they seem to indicate one register sets the clock Hi level period duration, and the other sets the clock Low level period duration.   But in the '704 doc, the Hi & Low registers are described as a combined 16-bit value {R07, R08}={LSB, MSB}.  The formulas differ too.

  (a)  is it true the '700 vs '704 ICs have different methods of setting I2C clocking ... or am I
        just reading things strangely?  The fact the reset defaults btwn '700 and '704 IC are
        different is interesting.

  (b)  It looks like docs for either '700 or '704 indicate 369-375 khz is maximum I2C clock rate.
        Any way to get to std 400 khz clock rate?


5.  Is there any ability for '700/'704 to be an I2C slave?


Thanks for any clarifications.


Bill
San Jose, CA  USA
 

[diazmarin09]

Hello Bill,

I hope all is great with you. Thank you for using the NXP communities.

1. In this case, the status of the SC18IM704 device remains active, while the status of the SC18IM700 is obsolete. I do recommend considering the SC18IM704PW for your design.
2. SC18IM704 is a functional replacement for SC18IM700 with exception of:

• New pinout
• GPIO no longer has quasi bidirectional mode
• Lower operating supply voltage level (1.71 V vs 2.4 V)
• Temperature range of -40 to +105 °C vs -40 to +85 °C
• Device is rotated 180 degrees in the tape pocket; pin 1 is now in Quadrant 1

3. We do guarantee a baud rate up to 460.8 kbit/s. It is a reliable setting.
4. You are correct, on each device, the I2C serial clock frequency is configured differently.

I do recommend using the SC18IM704-EVB evaluation board user guide (4.4 Sample control sequences from UART host) as a reference for your design.

The High-speed I2C-bus is 400 kbit/s. The registers must be configured accordingly.

5. The device acts as a master.

I hope this information helps.

Regards,

David

[wmwiese]

David,
Kind thanks for reply with details.  Am happy the UART runs reliably @ 460.8kbps.

Quick follow-up questions:

• Does the 'V' version info command work on the (older/prior) '700 chip?
  
  [If not, does it cause abnormal operation if used on older '700 chip?]
  
  
• Does the '704 (or '700) as master work with I2C slave devices which
  may use "clock stretching"?
  
  
• Is there anyway to get 400Khz I2C clocking on the '704??  (...instead of
  supposedly max 375 KHz?)

Thanks,
Bill 
San Jose

[diazmarin09]

Hello Bill,

Once again, thank you for using the NXP community.

1. The Read version function ID is not available on the SC18IM700 device.
2. Clock stretching is a feature of some targets. I am afraid it is not available in the SC18IM700/ SC18IM704 devices.
3. My apologies for the misunderstanding. The maximum I2C-bus clock frequency is 375kHz.

I hope this information helps.

Regards,

David