TMS320F28027: How to transmit 24bit data over SPI

Nishant Sharma72

Part Number: TMS320F28027
Other Parts Discussed in Thread: DAC8760

For my project, I am interfacing DAC8760 with F28027 through SPI. But as the data frame for DAC8760 is 24 bit and in F28027 we can only configure it up to 16bit. So my question is how to transmit 24 bits through SPI before enabling latch as it is clearly written in 8760 datasheet that only 24SCLK pulses must be provided before rising edge of the LATCH.

over 8 years ago

0 Mark Labbato over 8 years ago

Guru 30330 points

Please see my response on this thread:
e2e.ti.com/.../2535385

Thanks,
Mark

0 Nishant Sharma72 over 8 years ago in reply to Mark Labbato

Intellectual 780 points

I can use 8-bit frame length. But what about the SPISTEA pin. It will be high after the first transmission and the data will be latched which is incorrect.

0 Mark Labbato over 8 years ago in reply to Nishant Sharma72

Guru 30330 points

Nishant,
You have two options here:
1. The SPI will hold SPISTE low until the last data word has been transmitted. If you use the FIFO and write 3 8-bit words, the full 24 bits will be transmitted before SPISTE becomes inactive.
2. Use a GPIO and manually drive the Latch pin. before and after sending the 3 words. - there are other threads describing this on the forum. you should be able to search and find them.

Thanks,
Mark

0 Nishant Sharma72 over 8 years ago in reply to Mark Labbato

Intellectual 780 points

Thanks a lot for your prompt reply.

0 Mark Labbato over 8 years ago in reply to Nishant Sharma72

Guru 30330 points

Glad to help. Happy coding!

-Mark

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TMS320F28027: How to transmit 24bit data over SPI