Is there a chip that combines both a single channel MOSI tri-state & CS pull-up?

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MichaelMeissner

Senior Member+
According to the SPI guide:

Two hardware related issues are:
  • Add pull-up resistors for the CS pin (and D/C pin if used);
  • Make the MOSI pin for the device tri-state.

I'm wondering if there is a single chip that combines both. I would imagine you would connect CS and MOSI inputs on one side and get CS and MOSI outputs on the other (presumably with VCC and ground thrown in).

Something like:
Code:
Originally the connection would look like:

       Teensy            Device
       ------            -----
       3.3v -----------> Vdd
       Ground ---------> Ground
       MOSI -----------> MOSI
       SCK ------------> SCK
       CS -------------> CS
       MISO -----------> MISO

With pull-up resistors this would become:

       Teensy                            Device
       ------                            -----
       3.3v ---------------------------> Vdd
       Ground -------------------------> Ground
       MOSI ---------------------------> MOSI
       SCK ----------------------------> SCK
       CS ---+-------------------------> CS
             |
             +---- 2.2k resistor ---> Vdd

       MISO ---------------------------> MISO


If we have to add a a tri-state buffer this would logically be something like:

       Teensy                                     Device
       ------                                     ------
       3.3v ------------------------------------> Vdd
       Ground ----------------------------------> Ground
       MOSI ------------------------------------> MOSI
       SCK -------------------------------------> SCK
       CS ---+----------------------------------> CS
             |
             +---- 2.2k resistor ---> Vdd
	     |
	     +--- OE --> +----------+
                         |          |
       MISO ----> A ---> + tristate +--- Y -----> MISO
                         |          |
              Ground --> +          +
                         |          |
              Vdd -----> +----------+

So I'm wondering if there is a combined chip:

       Teensy                                         Device
       ------                                         ------
       3.3v ----------------------------------------> Vdd
       Ground --------------------------------------> Ground
       MOSI ----------------------------------------> MOSI
       SCK -----------------------------------------> SCK


                      +-------------------+
                      |                   |
       3.3v ---> Vdd -+--> +----------+
                           |          |   |
                      +----+ 2.2k ----+ <-+
                      |    |          |
       CS -----> OE --+--> + -------- +-------------> CS
                           |          |
       MISO ---> A ------> + tristate +--> Y -------> MISO
                           |          |
       Ground -----------> +----------+

Preferably in through hole or SOIC-8 (SOIC-6 if it exists). The primary motivation is to save real estate on my prototype boards, but not have to go to custom PCBs, or PCBs smaller than I can solder.
 
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