MCF8316AEVM: Read values from RAM (Volatile) Register Map by Code CCS

Hi Vuong,

The RAM registers can be accessed using the same I2C read/write commands in the HardwareI2C_MSP430FR2355_MCF8316AEVM.

However, to access the ALGORITHM_VARIABLE RAM registers, the code needs to be slightly modified since the algorithm variable addresses are 12-bit instead of 8-bit.

When constructing the control word in the I2C command, the lines:

line 143    // Construct the 24 bit control word (refer to datasheet section 7.6.2.1)
line 144    char control_word[3] = {0x10, 0x00, addr&0xFF};

line 222    // Construct the 24 bit control word (refer to datasheet section 7.6.2.1)
line 223    char control_word[3] = {0x90, 0x00, addr&0xFF};

needs to be changed to:

line 143    // Construct the 24 bit control word (refer to datasheet section 7.6.2.1)
line 144    char control_word[3] = {0x10, (addr&0x0000FF00)>>8, addr&0x000000FF};

line 222    // Construct the 24 bit control word (refer to datasheet section 7.6.2.1)
line 223    char control_word[3] = {0x90, (addr&0x0000FF00)>>8, addr&0x000000FF};

Please find the updated CCS project: 7444.HardwareI2C_MSP430FR2355_MCF8316AEVM.zip

Then the I2C_read32() can be used to read from the algorithm variable registers, such as:

I2C_read32(0x210, &result_var, I2C_TIMEOUT);

To set the speed reference through I2C, you simply need to

• set the PIN_CONFIG.SPEED_MODE register to 'Register Override mode'
  
• control speed reference by setting the ALGO_CTRL1.DIGITAL_SPEED_CTRL register
  

Regards,
Eric C.

Hi Vuong,

The source code of the I2C_read32() is contained within the main.c file of the CCS project that I've attached in my response above.

Example code to set the OVERRIDE bit and change DIGITAL_SPEED_CTRL to 10%, 53%, and 100%:

    // Temporary variable
    long read_result;
    
    // First read the PIN_CONFIG register so that we don't affect other bits when setting SPEED_MODE
    I2C_read32(0xA4, &read_result, I2C_TIMEOUT);
    
    // Set the PIN_CONFIG.SPEED_MODE bitfield to Register Override Mode (2h) while retaining other bits
    I2C_write32(0xA4, (read_result & (~0x00000003)) | 0x00000002, I2C_TIMEOUT);
    
    /*
     * DIGITAL_SPEED_CTRL is 15-bits, so max value is 32767 = 100% speed cmd
     * Multiply 32767 by speed cmd percentage, then bit shift left by 16 before writing to ALGO_CTRL1 register
     */
    
    // Set the ALGO_CTRL1.DIGITAL_SPEED_CTRL bitfield to 10%
    I2C_write32(0xEC, ((int)(0.10 * 32767)) << 16, I2C_TIMEOUT);
    
    // Set the ALGO_CTRL1.DIGITAL_SPEED_CTRL bitfield to 53%
    I2C_write32(0xEC, ((int)(0.53 * 32767)) << 16, I2C_TIMEOUT);
    
    // Set the ALGO_CTRL1.DIGITAL_SPEED_CTRL bitfield to 100%
    I2C_write32(0xEC, ((int)(1.00 * 32767)) << 16, I2C_TIMEOUT);

Example code to read Algorithm Variables such as the ALGORITHM_STATE and SPEED_FDBK:

    // Temporary variable
    long read_result;
    
    // Read ALGORITHM_STATE algorithm variable
    I2C_read32(0x210, &read_result, I2C_TIMEOUT);
    
    // Read SPEED_FDBK algorithm variable
    I2C_read32(0x752, &read_result, I2C_TIMEOUT);

Regards,
Eric C.

Hi Vuong,

Each RAM algorithm variables have their own ways of being interpreted from register hex value into the final meaningful unit. Please refer to the datasheet description of each of the algorithm variable for what additional calculation is needed to convert the value of each variable from the register hex value into the corresponding unit.

For instance, for the SPEED_FDBK register:

You would need to divide the read_result by 2^(27) then multiply by the value that's configured in the CLOSED_LOOP4.MAX_SPEED register in order to obtain the final estimated speed in Hz.

Regards,
Eric C.