📄 smbus_slave_f30x.c
字号:
//------------------------------------------------------------------------------------
//
// Copyright 2003 Cygnal Integrated Products, Inc.
//
// FILE NAME : SMBus_Slave_F30x.c
// TARGET DEVICE : C8051F300
// CREATED ON : 01/02
// CREATED BY : JS
//
// Revision 1.1 (11/18/02)
//
// Example software to demonstrate the C8051F30x SMBus interface in Slave mode
// - Interrupt-driven SMBus implementation
// - Only slave states defined
// - 1-byte SMBus data holder used for both transmit and receive
// - Timer1 used as SMBus clock rate (used only for free timeout detection)
// - Timer2 used by SMBus for SCL low timeout detection
// - Pinout:
// P0.0 -> SDA (SMBus)
// P0.1 -> SCL (SMBus)
// P0.2 -> unused
// P0.3 -> SW2
// P0.4 -> unused
// P0.5 -> unused
// P0.6 -> unused
// P0.7 -> C2D (debug interface)
//
//------------------------------------------------------------------------------------
// Includes
//------------------------------------------------------------------------------------
#include <c8051f300.h> // SFR declarations
#include <stdio.h>
//------------------------------------------------------------------------------------
// Global Constants
//------------------------------------------------------------------------------------
#define SYSCLK 24500000 // System clock frequency
#define SMB_FREQUENCY 50000 // Target SMBus frequency
#define WRITE 0x00 // SMBus WRITE command
#define READ 0x01 // SMBus READ command
#define SLA_ADD 0xF0 // Device addresses (7 bits, lsb is a
// don't care)
// Status vector - top 4 bits only
#define SMB_SRADD 0x20 // (SR) slave address received
// (also could be a lost arbitration)
#define SMB_SRSTO 0x10 // (SR) STOP detected, or lost
// arbitration
#define SMB_SRDB 0x00 // (SR) data byte received, or lost
// arbitration
#define SMB_STDB 0x40 // (ST) data byte transmitted
#define SMB_STSTO 0x50 // (ST) STOP detected
//-----------------------------------------------------------------------------------
//Global VARIABLES
//-----------------------------------------------------------------------------------
unsigned char SMB_DATA; // Global holder for SMBus data.
// All receive data is written here;
// all transmit data is read from here
bit DATA_READY; // Set to '1' by the SMBus ISR when
// a new data byte has been received.
// 16-bit SFR declarations
sfr16 TMR2RL = 0xca; // Timer2 reload registers
sfr16 TMR2 = 0xcc; // Timer2 counter registers
sbit LED = P0^2;
//-----------------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------------
void SMBus_Init (void);
void Timer1_Init (void);
void Timer2_Init (void);
void Port_Init (void);
void SMBus_ISR (void);
void Timer2_ISR (void);
//-----------------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------------
//
// Main routine performs all configuration tasks, then waits for SMBus communication.
void main (void)
{
PCA0MD &= ~0x40; // WDTE = 0 (Disable watchdog timer)
OSCICN |= 0x03; // Set internal oscillator to highest
// setting
Port_Init (); // Initialize Crossbar and GPIO
Timer1_Init(); // Configure Timer1 for use with SMBus
// free timeout detect
Timer2_Init (); // Configure Timer2 for use with SMBus
// low timeout detect
SMBus_Init (); // Configure and enable SMBus
EIE1 |= 1; // SMBus interrupt enable
IE |= 0x20; // Timer2 interrupt enable
EA = 1; // Global interrupt enable
SMB_DATA = 0xFD; // Initialize SMBus data holder
while(1)
{
while(!DATA_READY); // New SMBus data received?
DATA_READY = 0;
}
}
//------------------------------------------------------------------------------------
// Initialization Routines
//------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------
// SMBus_Init()
//------------------------------------------------------------------------------------
//
// SMBus configured as follows:
// - SMBus enabled
// - Slave mode enabled
// - Setup and hold time extensions enabled
// - Free and SCL low timeout detection enabled
//
void SMBus_Init (void)
{
SMB0CF = 0x1D; // Use Timer1 overflows as SMBus clock
// source
// Enable slave mode
// Enable setup & hold time extensions
// Enable SMBus Free timeout detect
// Enable SCL low timeout detect
SMB0CF |= 0x80; // Enable SMBus;
}
//------------------------------------------------------------------------------------
// Timer2_Init()
//------------------------------------------------------------------------------------
//
// Timer2 configured for use by the SMBus low timeout detect feature as follows:
// - Timer2 in 16-bit auto-reload mode
// - SYSCLK/12 as Timer2 clock source
// - Timer2 reload registers loaded for a 25ms overflow period
// - Timer2 pre-loaded to overflow after 25ms
// - Timer2 enabled
//
void Timer2_Init (void)
{
TMR2CN = 0x00; // Timer2 configured for 16-bit
// auto-reload, low-byte interrupt
// disabled
TMR2 = -(SYSCLK/12/40); // Timer2 configured to overflow after
TMR2RL = -(SYSCLK/12/40); // ~25ms (for SMBus low timeout detect)
CKCON &= ~0x20; // Timer2 uses SYSCLK/12
TR2 = 1; // Start Timer2
}
//------------------------------------------------------------------------------------
// Timer1_Init()
//------------------------------------------------------------------------------------
//
// Timer1 configured as the SMBus clock source (for free timeout detection):
// - Timer1 in 8-bit auto-reload mode
// - SYSCLK / 12 as Timer1 clock source
// - Timer1 overflow rate => 3 * SMB_FREQUENCY
// - Free timeout period will be ~10 * Timer1 overflow rate
// - Timer1 enabled
//
void Timer1_Init (void)
{
CKCON &= ~0x13; // Timer1 clock source = SYSCLK / 12
TMOD = 0x02; // Timer1 in 8-bit auto-reload mode
TH1 = -(SYSCLK/SMB_FREQUENCY/12/3); // Timer1 configured to overflow at 1/3
// the rate defined by SMB_FREQUENCY
TL1 = -(SYSCLK/SMB_FREQUENCY/12/3); // Timer1 preloaded to overflow at the
// rate defined by SMB_FREQUENCY
TR1 = 1; // Timer1 enabled
}
//------------------------------------------------------------------------------------
// PORT_Init
//------------------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports.
// P0.0 - SDA
// P0.1 - SCL
// P0.2 -
// P0.3 -
// P0.4 -
// P0.5 -
// P0.6 -
// P0.7 - C2D
//
void Port_Init (void)
{
XBR0 = 0x00; // No pins skipped
XBR1 = 0x04; // Enable SMBus pins
XBR2 = 0x40; // Enable crossbar and weak pull-ups
P0MDIN = 0xFF; // All P0 pins digital input
P0MDOUT = 0x00; // All P0 pins open-drain output
P0 = 0xFF; //
}
//------------------------------------------------------------------------------------
// Interrupt Service Routines
//------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------
// SMBus Interrupt Service Routine (ISR)
//------------------------------------------------------------------------------------
//
// SMBus ISR state machine
// - Slave only implementation - no master states defined
// - All incoming data is written to global variable <SMB_DATA>
// - All outgoing data is read from global variable <SMB_DATA>
//
void SMBUS_ISR (void) interrupt 6
{
bit RXTX; // Software flag for slave
// receiver-to-transmitter transition
switch (SMB0CN & 0xF0) // Decode the SMBus status vector
{
// Slave Receiver: Start+Address received
case SMB_SRADD:
if((SMB0DAT&0xFE) == SLA_ADD) // Decode address
{ // If the received address matches,
STA = 0; // Clear STA bit
ACK = 1; // ACK the received slave address
if(SMB0DAT&0x01==READ) // If the transfer is a master READ,
{
SMB0DAT = SMB_DATA; // Prepare outgoing byte
if(!(SMB0DAT&0x80)) // If data byte MSB = '0',
{
STO = 1; // Set STO to force outgoing MSB => '0'
RXTX = 1; // Set receiver-to-transmitter flag
}
}
}
else // If received slave address does not
{ // match,
ACK = 0; // NACK received address
}
break;
// Slave Receiver: Data received
case SMB_SRDB:
SMB_DATA = SMB0DAT; // Store incoming data
DATA_READY = 1; // Indicate new data received
ACK = 1; // ACK received data
break;
// Slave Receiver: Stop received
case SMB_SRSTO:
STO = 0; // STO must be cleared by software when
// a STOP is detected as a slave
break;
// Slave Transmitter: Data byte transmitted
case SMB_STDB:
// No action required;
// one-byte transfers
// only for this example
break;
// Slave Transmitter: Arbitration lost, Stop detected
case SMB_STSTO:
break; // No action required
// Default: all other cases undefined
default:
SMB0CN &= ~0x40; // Reset communication.
SMB0CN |= 0x40;
break;
}
SI=0; // Clear SMBus interrupt flag
if (RXTX) // If RXTX flag is set, the last state
{ // was a receiver-to-transmitter
// transition;
while(!TXMODE); // Wait for slave to enter transmit mode,
STO = 0; // Clear the STO bit and the RXTX flag
RXTX = 0;
}
}
//-----------------------------------------------------------------------------------
// Timer2 Interrupt Service Routine (ISR)
//-----------------------------------------------------------------------------------
//
// A Timer2 interrupt indicates an SMBus SCL low timeout.
// The SMBus is disabled and re-enabled here
//
void Timer2_ISR (void) interrupt 5
{
SMB0CN &= ~0x40; // Disable SMBus
SMB0CN |= 0x40; // Re-enable SMBus
TF2H = 0; // Clear Timer2 interrupt-pending flag
}⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -