Jump to content

16-bit USCI SPI transfers

Recommended Posts

I am trying to re-create this using USCI instead of USI. As seen there, USI can do 16-bit SPI transfers, which is needed to drive the MAX6957. Here is a small hint that USCI too is capable of 16-bit transfers, however I can't find anything related in the x2xx family guide nor the 2553 (which I'm trying to bend to my will) datasheet.


Can USCI (SPI) do 16(or more maybe)-bit transfers?

Link to post
Share on other sites

Yes, any multiple of 7 or 8 bits.


For many SPI peripherals, the SS or CS line is used to reset the internal SPI shift register. So to send a packet to the chip, assert SS, send one or more 7 or 8 bit chunks, and then deassert SS.


Note that the STEN line is always an input and is used for optional muti-master arbitration in master mode. It is not used to control SS/CS of slaves on the bus. 4 wire master mode is not the same as a 4 wire SPI connection.

Link to post
Share on other sites

The USI has 1 16bit register that can be addressed as 2 8bit registers for i2c transfers.


The USCI does not.

The shift registers hold bytes in the USCI so there is no option for 16-bit transfers. Instead,the UC7BIT can be set for 7-bit transfers, although I never encountered anything that usesthis (it is more applicable to UART mode).

This is from the MSP430 Microcontroller Basics book.


Link to post
Share on other sites

My problem was actually with the concept of how to drive SS. Many have tried to explain that if the MSP is the master, SS will need to be driven manually and not left to USCI (USI), but for some reason it didn't really sink in until oPossum chimed in :).


My thickness can be astronomical at times :).

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...