初學者:請大家?guī)兔Γ。。。。?[2shift] [26次] 01-8-8 下午 03:40:25
我想用80c196kc的高速輸入口和高速輸出口模擬一個全雙工的串口,該怎么來實現(xiàn)?
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網(wǎng)上找到的,應該可以參考 [power27] [22次] 01-8-8 下午 04:41:04 
IAR Application Note G - 001
1
IAR Application Note G - 001
Generic Software Uart
written in C
SUMMARY
This application note details a generic software UART written in C which
can be implemented on any microprocessor with a C compiler. It requires a
timer interrupt to be set to 3 times the baud rate, and two software-controlled
pins for the receive and transmit functions.
KEYWORDS
UART, C code
The Problem to be solved
Software UARTs are generally coded in assembly for speed purposes, but
with the increasing speed of processors, a software UART written in C is now
easily implemented and highly portable.
The Difficulties Involved
The implementation has three fundamental requirements:
1. A compiler must exist for the microprocessor.
2. A timer interrupt must be set to interrupt at three times the required
baud rate. Most microprocessors have a timer interrupt that can be
used for this, or an external clock interrupt could be used to achieve
the same goal.
3. There must be a transmit pin which can be set from the software, and a
receive pin which can be read by the software.
The Solution
The C source file must be linked into the user’s application with the necessary
interface routines listed as follows:
1. void get_rx_pin_status( void )
Returns 0 or 1 dependent on whether the receive pin is high or low.
2. void set_tx_pin_high( void )
Sets the transmit pin to the high state.
3. void set_tx_pin_low( void )
Sets the transmit pin to the low state.
4. void idle( void )
Background functions to execute while waiting for input.
5. void timer_set( int BAUD_RATE )
Sets the timer to 3 times the baud rate.
// UART.C
//
// Generic software uart written in C, requiring a timer set to 3 times
// the baud rate, and two software read/write pins for the receive and
// transmit functions.
//
// * Received characters are buffered
// * putchar(), getchar(), kbhit() and flush_input_buffer() are available
// * There is a facility for background processing while waiting for input
//
// Colin Gittins, Software Engineer, Halliburton Energy Services
//
// The baud rate can be configured by changing the BAUD_RATE macro as
// follows:
//
// #define BAUD_RATE            19200.0
//
// The function init_uart() must be called before any comms can take place
//
// Interface routines required:
// 1. get_rx_pin_status()
//    Returns 0 or 1 dependent on whether the receive pin is high or low.
// 2. set_tx_pin_high()
//    Sets the transmit pin to the high state.
// 3. set_tx_pin_low()
//    Sets the transmit pin to the low state.
// 4. idle()
//    Background functions to execute while waiting for input.
// 5. timer_set( BAUD_RATE )
//    Sets the timer to 3 times the baud rate.
// 6. set_timer_interrupt( timer_isr )
//    Enables the timer interrupt.
//
// Functions provided:
// 1. void flush_input_buffer( void )
//    Clears the contents of the input buffer.
// 2. char kbhit( void )
//    Tests whether an input character has been received.
// 3. char getchar( void )
//    Reads a character from the input buffer, waiting if necessary.
// 4. void turn_rx_on( void )
//    Turns on the receive function.
// 5. void turn_rx_off( void )
//    Turns off the receive function.
// 6. void putchar( char )
//    Writes a character to the serial port.

#include <stdio.h>

#define BAUD_RATE        19200.0

#define IN_BUF_SIZE        256

#define TRUE 1
#define FALSE 0

static unsigned char        inbuf[IN_BUF_SIZE];
static unsigned char        qin = 0;
static unsigned char        qout = 0;

static char             flag_rx_waiting_for_stop_bit;
static char             flag_rx_off;
static char             rx_mask;
static char             flag_rx_ready;
static char             flag_tx_ready;
static char             timer_rx_ctr;
static char             timer_tx_ctr;
static char             bits_left_in_rx;
static char             bits_left_in_tx;
static char             rx_num_of_bits;
static char             tx_num_of_bits;
static char            internal_rx_buffer;
static char            internal_tx_buffer;
static char            user_tx_buffer;

void timer_isr(void)
    {
    char            mask, start_bit, flag_in;

// Transmitter Section
    if ( flag_tx_ready )
        {
        if ( --timer_tx_ctr<=0 )
            {
            mask = internal_tx_buffer&1;
            internal_tx_buffer >>= 1;
            if ( mask )
                {
                set_tx_pin_high();
                }
            else
                {
                set_tx_pin_low();
                }
            timer_tx_ctr = 3;
            if ( --bits_left_in_tx<=0 )
                {
                flag_tx_ready = FALSE;
                }
            }
        }
// Receiver Section
    if ( flag_rx_off==FALSE )
        {
        if ( flag_rx_waiting_for_stop_bit )
            {
            if ( --timer_rx_ctr<=0 )
                {
                flag_rx_waiting_for_stop_bit = FALSE;
                flag_rx_ready = FALSE;
                internal_rx_buffer &= 0xFF;
                if ( internal_rx_buffer!=0xC2 )
                    {
                    inbuf[qin] = 
internal_rx_buffer;
                    if ( ++qin>=IN_BUF_SIZE )
                        {
                        qin = 0;
                        }
                    }
                }
            }
        else        // rx_test_busy
            {
            if ( flag_rx_ready==FALSE )
                {
                start_bit = get_rx_pin_status();
// Test for Start Bit
                if ( start_bit==0 )
                    {
                    flag_rx_ready = TRUE;
                    internal_rx_buffer = 0;
                    timer_rx_ctr = 4;
                    bits_left_in_rx = 
rx_num_of_bits;
                    rx_mask = 1;
                    }
                }
            else    // rx_busy
                {
                if ( --timer_rx_ctr<=0 )
                    {        
        // rcv
                    timer_rx_ctr = 3;
                    flag_in = 
get_rx_pin_status();
                    if ( flag_in )
                        {
                    
    internal_rx_buffer |= rx_mask;
                        }
                    rx_mask <<= 1;
                    if ( --
bits_left_in_rx<=0 )
                        {
                    
    flag_rx_waiting_for_stop_bit = TRUE;
                        }
                    }
                }
            }
        }
    }

void init_uart( void )
    {
    flag_tx_ready = FALSE;
    flag_rx_ready = FALSE;
    flag_rx_waiting_for_stop_bit = FALSE;
    flag_rx_off = FALSE;
    rx_num_of_bits = 10;
    tx_num_of_bits = 10;

    set_tx_pin_low();

    timer_set( BAUD_RATE );
    set_timer_interrupt( timer_isr );     // Enable timer interrupt
    }

char _getchar( void )
    {
    char        ch;

    do
        {
        while ( qout==qin )
            {
            idle();
            }
        ch = inbuf[qout] & 0xFF;
        if ( ++qout>=IN_BUF_SIZE )
            {
            qout = 0;
            }
        }
    while ( ch==0x0A || ch==0xC2 );
    return( ch );
    }

void _putchar( char ch )
    {
    while ( flag_tx_ready );
    user_tx_buffer = ch;

// invoke_UART_transmit
    timer_tx_ctr = 3;
    bits_left_in_tx = tx_num_of_bits;
    internal_tx_buffer = (user_tx_buffer<<1) | 0x200;
    flag_tx_ready = TRUE;
    }

void flush_input_buffer( void )
    {
    qin = 0;
    qout = 0;
    }

char kbhit( void )
    {
    return( qin!=qout );
    }

void turn_rx_on( void )
    {
    flag_rx_off = FALSE;
    }

void turn_rx_off( void )
    {
    flag_rx_off = TRUE;
    }


謝謝您! [2shift] [1次] 01-8-8 下午 04:49:25 

 
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