I/O口例程：
F12x_Ports_SwitchLED.c
//-----------------------------------------------------------------------------
// Copyright 2005 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program demonstrates how to configure port pins as digital inputs
// and outputs. The C8051F120 target board has one push-button switch
// connected to a port pin and one LED. The program constantly checks the
// status of the switch and if it is pushed, it turns on the LED.
//
// The program also monitors P4.0. If P4.0 is high, it sets P4.1 low. If
// P4.0 is low, P4.1 is set high. The purpose of this part of the program
// is to show how to access the higher ports. Ports 4-7 are not available
// on all SFR pages, so the SFRPAGE register must be set correctly before
// reading or writing these ports.
//
//
// How To Test:
//
// 1) Download code to a 'F120 target board
// 2) Ensure that the J1 and J3 headers are shorted
// 3) Push the button (P3.7) and see that the LED turns on
// 4) Set P4.0 high and low using an external connection and check that
// the output on P4.1 is the inverse of P4.0
//
//
// FID: 12X000004
// Target: C8051F12x
// Tool chain: Keil C51 7.50 / Keil EVAL C51
// Command Line: None
//
// Release 1.0
// -Initial Revision (GP)
// -15 NOV 2005
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include <c8051f120.h> // SFR declarations
//-----------------------------------------------------------------------------
// Pin Declarations
//-----------------------------------------------------------------------------
sbit LED1 = P1^6; // LED1 ='1' means ON
sbit SW1 = P3^7; // SW1 ='0' means switch pressed
sbit INPUT1 = P4^0; // port pin 4.0
sbit OUTPUT1 = P4^1; // port pin 4.1
//-----------------------------------------------------------------------------
// Function Prototypes
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void);
void PORT_Init (void);
//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------
void main (void)
{
WDTCN = 0xde; // Disable watchdog timer
WDTCN = 0xad;
PORT_Init(); // Initialize Port I/O
OSCILLATOR_Init (); // Initialize Oscillator
while (1)
{
if (SW1 == 0) // If switch depressed
{
LED1 = 1; // Turn on LED
}
else
{
LED1 = 0; // Else, turn it off
}
SFRPAGE = CONFIG_PAGE; // set SFR page before reading or writing
// to P4 registers
if (INPUT1 == 0) // If input is low
{
OUTPUT1 = 1; // Make OUTPUT1 inverse of INPUT1
}
else
{
OUTPUT1 = 0; // Make OUTPUT1 inverse of INPUT1
}
} // end of while(1)
} // end of main()
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// OSCILLATOR_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function initializes the system clock to use the internal oscillator
// at its maximum frequency.
//
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE; // Save Current SFR page
SFRPAGE = CONFIG_PAGE; // set SFR page
OSCICN |= 0x03; // Configure internal oscillator for
// its maximum frequency (24.5 Mhz)
SFRPAGE = SFRPAGE_SAVE; // Restore SFR page
}
//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function configures the crossbar and ports pins.
//
// To configure a pin as a digital input, the pin is configured as digital
// and open-drain and the port latch should be set to a '1'. The weak-pullups
// are used to pull the pins high. Pressing the switch pulls the pins low.
//
// To configure a pin as a digital output, the pin is configured as digital
// and push-pull.
//
// Some ports pins do not have the option to be configured as analog or digital,
// so it not necessary to explicitly configure them as digital.
//
// An output pin can also be configured to be an open-drain output if system
// requires it. For example, if the pin is an output on a multi-device bus,
// it will probably be configured as an open-drain output instead of a
// push-pull output. For the purposes of this example, the pin is configured
// as push-pull output because the pin in only connected to an LED.
//
// P1.6 digital push-pull LED1
// P3.7 digital open-drain Switch 1
// P4.0 digital open-drain Input 1
// P4.1 digital push-pull Output 1
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE; // Save Current SFR page
SFRPAGE = CONFIG_PAGE; // set SFR page before writing to
// registers on this page
P1MDIN |= 0x40; // P1.6 is digital
P1MDOUT = 0x40; // P1.6 is push-pull
P3MDOUT = 0x00; // P3.7 is open-drain
P3 |= 0x80; // Set P3.7 latch to '1'
P4MDOUT = 0x02; // P4.0 is open-drain; P4.1 is push-pull
P4 = 0x01; // Set P4.1 latch to '1'
XBR2 = 0x40; // Enable crossbar and enable
// weak pull-ups
SFRPAGE = SFRPAGE_SAVE; // Restore SFR page
}
//-----------------------------------------------------------------------------
// End Of File
//----------------------------------------------------------------------------- |
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