I think it depends a lot on how fast your interrupt service routine winds
being. If you have total control over bit times and inter-character-gaps on
the sending device, you could make it as fast or as slow as your DSP chip
I doubt if the "line speed" of the SPI peripherals will be the limit. The
56803 went to something like 1-5 MHz, if you could keep up. The gap between
characters has to be long enough for you to capture the data.
Your ISR has to be faster than one character-time. I don't know your chip,
or your ISR-dispatcher, but interrupt response time might be in the .5 to 3
microsecond range, and your ISR might be in the .5 to 33 microsecond range. That might mean anywhere between 1-33 usec per character (30-1000 Kwords per
However, you won't know until you can time your ISR. I tried to do too much
in a SPIbus ISR once, and regretted it.
From: gunala_sunitha [mailto:]
Sent: Thursday, December 30, 2004 1:24 PM
Subject: [motoroladsp] how to calculate the maximum rate for serial
ports of dsp56002/56303 hi-need a small help regarding the calculation of maximum rate that
a dsp 56002/56303 can read through the ssiport of dsp56002.and essi
as i want to interface the A/D chip to these devices.