SPI baudrate

Ken267

I just started with SPI and im confused as to how fast SPI can transfer data. If the propeller chip is running at 80MHz, will the baud rate be 80Mbps? In the SPI engine it said at 80 MHz the baud rate is 2.5M. What is the max SPI transfer speed?

hippy

Using the video hardware, waitvid, you can probably output SPI using two bits per bit to send ( set data, then transition the clock ), so that's half of whatever the maximum video clock rate is - 160MHz ? - 80Mbps.

Mike Green

With careful assembly coding, you can use a cog counter to produce the clock pulses needed and you might be able to process one bit in about 4 instruction times. That's 200ns or about 5Mbps for short bursts. The decision making between bytes can slow things down. I think 2.5M is about right for an overall throughput considering all sorts of other overhead.

Hippy,
That's a great idea for blind SPI transmission. Receiving is tougher (and slower), particularly if your device has some address / status / command bits thrown in or you have to do the simultaneous transmit/receive thing that many devices support.

Post Edited (Mike Green) : 10/28/2007 1:27:22 AM GMT