As with every other peripheral, we'll have to initialize this timer before we can use it. And just as in the previous section, initialization is going to involve two steps: powering up the timer and then configuring it.

Powering up the timer is easy: We just have to set TIM6EN bit to 1. This bit is in the APB1ENR register of the RCC register block.

# #![allow(unused_variables)]
#fn main() {
    // Power on the TIM6 timer
    rcc.apb1enr.modify(|_, w| w.tim6en().set_bit());
#}

The configuration part is slightly more elaborate.

First, we'll have to configure the timer to operate in one pulse mode.

# #![allow(unused_variables)]
#fn main() {
    // OPM Select one pulse mode
    // CEN Keep the counter disabled for now
    tim6.cr1.write(|w| w.opm().set_bit().cen().clear_bit());
#}

Then, we'll like to have the CNT counter operate at a frequency of 1 KHz because our delay function takes a number of milliseconds as arguments and 1 KHz produces a 1 millisecond period. For that we'll have to configure the prescaler.

# #![allow(unused_variables)]
#fn main() {
    // Configure the prescaler to have the counter operate at 1 KHz
    tim6.psc.write(|w| w.psc().bits(psc));
#}

I'm going to let you figure out the value of the prescaler, psc. Remember that the frequency of the counter is apb1 / (psc + 1) and that apb1 is 8 MHz.