From: Jim Brain (brain_at_jbrain.com)
Date: 2004-05-13 18:59:22
> True, but the timeouts in the protocol allow a software-based response. > Womo measured that my C2N232 solution has a delay of a few microseconds, > even though it responds to ATN with an interrupt. > Why? A microcontroller can easily do this with polling. At 38400 bps, > RS-232 receive interrupts can arrive every 260 µs. I've disabled the > RS-232 receive interrupts in some places in my serial bus code. Mine will come in every 21 uS (If I did the math right for 460Kbps), which is about 310 clocks on the CPU (roughly 310 instructions...) IP traffic on the controller could come in as well. I just don't want to poll, as there are such low latency IRQs available for me. > >> For more details (and source code) for this, have a look at the >> cbm4linux  >> project. That's the reason why a XE1541 cannot be used with cbm4linux, >> but a new XM1541 was introduced. > > On a multitasking computer, it's a completely different matter, as you > can't > tie the processor for long periods of time. There, it's better to use > interrupts (or delegate the serial bus handling to an external > microcontroller, > like the C2N232 with the serial bus modification). Yes, I agree. If I was working with NT or MacOS or Linux, it would be one story, but I already am biting the bullet to provide more adaptable interface HW. Right now, I am checking to see if the SPI interface in the AVR can be tweaked to do all of the bit-banging for me. Jim Message was sent through the cbm-hackers mailing list
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