My Documents/icctest/ASIO/asio_asm.c File Reference

#include "asio.h"

Functions
void	asio_handler (void)

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Detailed Description

• defines ASM implementation for an asynchronous serial IO driver for Propeller C bringup. See header file for more details.

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Function Documentation

void asio_handler

(

void

)

Handle transmit and receive here. Hard to make our deadline ... again :) LMM/Time lessons learned with beta preview:

• Don't ever use a C global with asm("...").
• Using globals for decisions takes lots of time. Use locals instead.
• Using function calls are expensive (figures) costs 2us for 80MHz prop.
• Using "if" in C code is also expensive costs 2us for 80MHz prop. Interestingly, if(--var) ... is cheaper than if(var) ....
• Use asm(test ... wz), asm(IF_Z ....) costs 1us for 80MHz prop.
• A while(1) costs 0.5us to 0.7us for 80MHz prop.
• A for(;;) costs 0.5us to 0.7us for 80MHz prop.
• Using too many local variables in a function can throw compiler errors.

Basic handler algorithm: Set time do work then waitcnt for remaining time to pass for time critical work. Setting/Saving a new rx/tx byte is not time critical; waitcnt there causes failure.

Get rx state. If rx state == mark (ASIO_RX_INVERTED) & rx not in progress, start new byte rx set new wait and continue Else if not tick time, decrement tick wait and continue

Else set tick to bit tick time If rx byte in progress, save bit to rxbyte wait and continue If tx byte in progress, set next bit from txbyte wait and continue Else if tx tail != head, load txbyte and tx start bit

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