ST9 datasheet(85/146 Pages) STMICROELECTRONICS

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ST9 USER GUIDE

as the Load register. The solution is to initialise the MFT with REG0R in capture mode by set-

ting the RM0 bit of the TCR register to ensure Free-Running Mode. When we need to load a

value in the counter, we temporarily clear the RM0 bit. Then we set REG0R to the value that

must be written in the counter. The CP0 bit in the FLAGR register is pulsed high to write the

contents of REG0R into the counter. Then we set bit RM0 again.

4.4.3.2 Initialisation

The code for initializing the MFT is given below.

Note:

The ICR register sets the input to Autodiscrimination mode. In this mode, the lower four bits are

irrelevant.

void ConfigTimer1 ( void )

{

SelectPage (T1D_PG) ;

T_REG0R = 0 ;/* This register is used to preload the counter */

T_REG1R = 0 ;/* This register is used to read the counter */

/* T_CMP0R and T_CMP1R are not used */

T_TCR = Tm_cen ;/* enable counter */

/* The counter will not start until the Global Counter Enable is set in

T_TMR = Tm_rm0 ;/* capture using REG0R and monitor using REG1R */

/* This mode is not desired, but is implies free-running, which we need

T_ICR = Tm_ab_aa ;/* inputs used in autodiscriminating mode */

/* For so, the port 3 must be set to input on pins P3.4 and P3.6 */

T_PRSR = 0 ;/* prescaler rate = 1 */

T_OACR = 0 ;/* output A not used */

T_OBCR = 0 ;/* output B not used */

T_FLAGR = 0 ;/* not used */

T_IDMR = 0 ;/* not used */

}

4.4.3.3 Reading

To read the value of the counter, you need to capture it in one of the registers, since the

counter itself does not have an address and cannot be read directly. There are two ways of

reading the counter:

Set one of the registers REG0R or REG1R to Capture mode. A pulse on bit CP0 or CP1, re-

spectively, transfers the contents of the counter to the corresponding register.

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