/home/daqweb/fgddaq/c8051/Protocols/temp36_SST_handler.c File Reference

#include "../mscbemb.h"
#include "temp36_SST_handler.h"

Functions
unsigned char	FCS_Step (unsigned int msg, unsigned char fcs) reentrant
void	SST_Init (int SST_LINE)
void	SST_Clear (int SST_LINE)
void	SST_DrvHigh (int SST_LINE)
void	SST_DrvLow (int SST_LINE)
unsigned char	SST_DrvClientResponse (int SST_LINE)
void	SST_WriteByte (unsigned char datByte, int SST_LINE)
unsigned char	SST_ReadByte (int SST_LINE)
Variables
sbit	SST1 = MSCB_SST1
sbit	SST2 = MSCB_SST2
unsigned char code	FCS_data []

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Function Documentation

unsigned char FCS_Step	(	unsigned int	msg,
		unsigned char	fcs
	)

Single calculation for 8-bit cyclic redundancy checksum usually used in FORWARD recursive format (to save code-space) Reentrant function /code

/endcode

Parameters:

	msg
	fcs

Returns:

FCS value (CRC-8 code)

                                                                      {
   return FCS_data[(msg ^ fcs)];
}

void SST_Clear

(

int

SST_LINE

)

Drives SST line to low for a reasonably long time which gives enough time for the SST to go idle.

                             {
  // Test this, high low high low
  if(SST_LINE==1)
     SST1 = 0;
  else if(SST_LINE==2)                                  
          SST2 = 0;
  delay_ms(SST_CLEAR_DELAY); //clear to 0's
}

unsigned char SST_DrvClientResponse

(

int

SST_LINE

)

Get the comparator bit value (Client response)

Returns:

Read Bit from Client's Response, Only 1 or 0 (gone through comparator)

                                                  {

  // Drive SST to logic "0" (high 1/4, low 3/4) to let Client
  // drive SST to its desired state
  if(SST_LINE==1)
  {
     SST1 = 1; //Drv high (originator drives SST bus high to toggle client's response
     delay_us (1);
     SST1 = 0;

     delay_us(T_BIT / 2.0); //delay for half of T_BIT time

#if defined(CPU_C8051F120)
     SFRPAGE  = CPT1_PAGE;      
#endif
     if(SST_ClientResponse1 == 1)
  //if the comparator output is high, then return 1
     {
        delay_us(2 * T_H0);
        return 1;
     }
     else
     //if the comparator output is low, then return 0
     {
        delay_us(2 * T_H0);
        return 0;
     }
   }
  else if(SST_LINE==2)
  {
     SST2 = 1; //Drv high (originator drives SST bus high to toggle client's response
     delay_us (1);
     SST2 = 0;

     delay_us(T_BIT / 2.0); //delay for half of T_BIT time

#if defined(CPU_C8051F120)
     SFRPAGE  = CPT0_PAGE;      
#endif
     if(SST_ClientResponse2 == 1)
  //if the comparator output is high, then return 1
     {
        delay_us(2 * T_H0);
        return 1;
     }
     else
     //if the comparator output is low, then return 0
     {
        delay_us(2 * T_H0);
        return 0;
     }
   }
}

void SST_DrvHigh

(

int

SST_LINE

)

Drives SST line to a logic "high" or "1", which is defined as driving SST high 3/4 cycle of t_Bit and the rest of it low

                               {
  // Drive high for 0.75 * T_BIT
  if(SST_LINE==1)
  {
     SST1 = 1;
     delay_us(T_H1);
     SST1 = 0; //drive the rest of T_BIT low
     delay_us(T_BIT - T_H1);
  }
  else if(SST_LINE==2)
  {
     SST2 = 1;
     delay_us(T_H1);
     SST2 = 0; //drive the rest of T_BIT low
     delay_us(T_BIT - T_H1);
  }

        
}

void SST_DrvLow

(

int

SST_LINE

)

To drive SST line to a logic "low" or "0", which is defined as driving SST high for 1/4 cycle of t_Bit and the rest of it low.

                              {
  // Drive high for 0.25 * T_BIT
  if(SST_LINE==1)
  {
     SST1 = 1;
     delay_us(T_H0);
     SST1 = 0; //drive the rest of T_BIT low
     delay_us(T_BIT - T_H0);
  }
  else if(SST_LINE==2)
  {
     SST2 = 1;
     delay_us(T_H0);
     SST2 = 0; //drive the rest of T_BIT low
     delay_us(T_BIT - T_H0);
  }   
}

void SST_Init

(

int

SST_LINE

)

Initialize the SST bus by issuing a CLEAR

                            {   
        //Clear the SST signals (drive Low for a certain period)
        SST_Clear(SST_LINE);
}

unsigned char SST_ReadByte

(

int

SST_LINE

)

Read a single byte from the SST device.

Returns:

Device Client byte response

                                         {
  unsigned char din = 0;
  unsigned char dataReceived = 0;
  signed char j = 0;

  for(j = 7; j >= 0; j--) {
    // Get single bit from comparator
    din = SST_DrvClientResponse(SST_LINE);
    dataReceived |= (din << j);
  }
  return dataReceived;
}

void SST_WriteByte	(	unsigned char	datByte,
		int	SST_LINE
	)

Write a single byte to the SST device.

Parameters:

datByte

                                                        {
  //declare local variables
  unsigned char toBeDrv = 0;
  int i = 0;
  SST_LINE &= 0xFF;

  if(SST_LINE==1)
  {
     for(i = 7; i >= 0; i--) //8bits in 1 byte
     {
        toBeDrv = (datByte >> i) & 0x1;
        if(toBeDrv == 0) //if the bit to be driven is logic 0
        {
           SST_DrvLow(SST_LINE);
        }
        else if(toBeDrv == 1) //if the bit to be driven is logic 1
        {
           SST_DrvHigh(SST_LINE);
        }
        else //if the bit to be driven is neither 0 nor 1
        {
           return; //error
        }
     }
   }
        else if(SST_LINE==2)
        {
      for(i = 7; i >= 0; i--) //8bits in 1 byte
      {
        toBeDrv = (datByte >> i) & 0x1;
        if(toBeDrv == 0) //if the bit to be driven is logic 0
        {
           SST_DrvLow(SST_LINE);
        }
        else if(toBeDrv == 1) //if the bit to be driven is logic 1
        {
           SST_DrvHigh(SST_LINE);
        }
        else //if the bit to be driven is neither 0 nor 1
        {
           return; //error
        }
      }
        }
}

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Variable Documentation

unsigned char code FCS_data[]

sbit SST1 = MSCB_SST1

sbit SST2 = MSCB_SST2

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