ST9 datasheet(86/146 Pages) STMICROELECTRONICS

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ST9 USER GUIDE

Put REG1R in Monitor mode. In this mode, REG1R continuously reflects the value of the

counter, without the need for pulsing a bit in a register.

In the stepper motor application, we have chosen to use Monitor mode. No special function is

needed to read the counter. A simple assignment of REG1R to a variable is enough, such as:

Pos = REG1R ;/* Get current counter value */

4.4.3.4 Updating

As mentioned in Section 4.5.3.1, updating requires switching the mode of REG0R from Cap-

ture to Load.

/* This function forces the MFT1 counter to a value given in argument */

void SetEncoder ( int Value )

{

SelectPage (T1D_PG) ;

T_TMR &= ~Tm_rm0 ;/* Switch temporarily to "Load with REG0R" mode */

T_REG0R = Value ;/* set encoder */

/* convert motor position to match the encoder's resolution */

T_FLAGR |= Tm_cp0 ;/* Load counter with this value by pulsing CP0 high */

T_FLAGR &= ~Tm_cp0 ;/* Return CP0 to low */

T_TMR |= Tm_rm0 ;/* Go back to "Capture with REG0R" mode that implies

free-running */

}

4.4.4 MFT Application 1: Generating 2 PWMs using Interrupts

This application generates 2 independent PWM signals on pins T0OUTA and T0OUTB pro-

vided that a logical low level is applied to gate T0INA. The outputs are reset on compare

events and set on the counter underflow. This application is found in the MFT/appli1 directory.

Counter compare interrupts are used to reload compare registers in order to modify the duty

cycle.

When running one of these three examples on an ST92F150 microcontroller, note that MFT

outputs are pure open drain.

4.4.5 MFT Application 2: Generating a PWM using DMA

This application generates a PWM signal on pin T0OUTA using a DMA channel to transfer

duty cycle data from memory to register COMP0. The DMA transfer only occurs once as it is

not re-initialized in the DMA end of block interrupt routine. This application is found in the MFT/

appli2.

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