CT Board

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====== Timer Compare ======

\\ {{timer_output.svg}} \\ \\

===== Configuration Registers =====

==== TIMx_CCMR1/2 - Capture/compare mode register 1/2 ====

\\ {{timer_reg_ccmr1.svg}} {{timer_reg_ccmr2.svg}} \\ \\

**Output compare mode**

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|OCxM|000|Frozen - The comparison between the output compare register TIMx_CCR1 and the counter TIMx_CNT has no effect on the outputs.(this mode is used to generate a timing base).|
|::: |001|Set channel 1 to active level on match. OC1REF signal is forced high when the counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).|
|::: |010|Set channel 1 to inactive level on match. OC1REF signal is forced low when the counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).|
|::: |011|Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.|
|::: |100|Force inactive level - OC1REF is forced low.|
|::: |101|Force active level - OC1REF is forced high.|
|::: |110|PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNT<TIMx_CCR1 else inactive. In downcounting, channel 1 is inactive (OC1REF=‘0’) as long as TIMx_CNT>TIMx_CCR1 else active (OC1REF=’1’).|
|::: |111|PWM mode 2 - In upcounting, channel 1 is inactive as long as TIMx_CNT<TIMx_CCR1 else active. In downcounting, channel 1 is active as long as TIMx_CNT>TIMx_CCR1 else inactive.|

**Input compare mode**

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|ICxF|0000|No filter, f<sub>DTS</sub> (reset state)|1000|f<sub>sampling</sub> => f<sub>DTS</sub> / 8, N=6|
|:::|0001|f<sub>sampling</sub> => f<sub>CKINT</sub>, N=2|1001|f<sub>sampling</sub> => f<sub>DTS</sub> / 8, N=8|
|:::|0010|f<sub>sampling</sub> => f<sub>CKINT</sub>, N=4|1010|f<sub>sampling</sub> => f<sub>DTS</sub> / 16, N=5|
|:::|0011|f<sub>sampling</sub> => f<sub>CKINT</sub>, N=8|1011|f<sub>sampling</sub> => f<sub>DTS</sub> / 16, N=6|
|:::|0100|f<sub>sampling</sub> => f<sub>DTS</sub> / 2, N=6|1100|f<sub>sampling</sub> => f<sub>DTS</sub> / 16, N=8|
|:::|0101|f<sub>sampling</sub> => f<sub>DTS</sub> / 2, N=8|1101|f<sub>sampling</sub> => f<sub>DTS</sub> / 32, N=5|
|:::|0110|f<sub>sampling</sub> => f<sub>DTS</sub> / 4, N=6|1110|f<sub>sampling</sub> => f<sub>DTS</sub> / 32, N=6|
|:::|0111|f<sub>sampling</sub> => f<sub>DTS</sub> / 4, N=8|1111|f<sub>sampling</sub> => f<sub>DTS</sub> / 32, N=8|
|ICxPSC|00|no prescaler, capture is done each time an edge is detected on the capture input (reset state)|
|:::  |01| capture is done once every 2 events|
|:::  |10| capture is done once every 4 events|
|:::  |11| capture is done once every 8 events|

**Select mode**

|CCxS|00|CCx channel is configured as output|
|::: |01|CCx channel is configured as input, ICx is mapped on TIx|
|::: |10|CCx channel is configured as input, ICx is mapped on TIx|
|::: |11|CCx channel is configured as input, ICx is mapped on TRC. This mode is working only if an internal trigger input is selected through TS bit (TIMx_SMCR register)|
|::: |  |//*Note: CCxS bits are writable only when the channel is OFF (CCxE = ‘0’ in TIMx_CCER).//|

==== TIMx_DIER - DMA / Interrupt enable register ====

\\ {{timer_reg_dier.svg}} \\ \\

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|CCxDE|0|CCx DMA request disabled (reset state)|
|:::  |1|CCx DMA request enabled|
|CCxIE|0|CCx interrupt disabled (reset state)|
|:::  |1|CCx interrupt enabled|

==== TIMx_CCER - Capture/compare enable register ====

\\ {{timer_reg_ccer.svg}} \\ \\

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|CCxNP|0|OC1N active high|
|::: |1|OC1N active low|
|CCxNE|0|Off - OC1N is not active. OC1N level is then function of MOE, OSSI, OSSR, OIS1, OIS1N and CC1E bits.|
|::: |1|On - OC1N signal is output on the corresponding output pin depending on MOE, OSSI, OSSR, OIS1, OIS1N and CC1E bits.|
|::: | |//*Note:   On channels having a complementary output, this bit is preloaded. If the CCPC bit is set in the TIMx_CR2 register then the CC1NE active bit takes the new value from the preloaded bit only when a Commutation event is generated.//|
|CCxP|0|OC1 active high|
|::: |1|OC1 active low|
|CCxE|0|Capture/compare output x disabled (reset state)|
|::: |1|Capture/compare output x enabled|

==== TIMx_CCRx - Capture/compare enable register ====

\\ {{timer_reg_ccrx.svg}} \\ \\

|< 100% 5em 5em >|
|CCRx|15:0|Capture/Compare value|

==== TIMx_BDTR - Break and dead-time register ====

\\ {{timer_reg_bdtr.svg}} \\ \\

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|MOE|0|OC and OCN outputs are disabled or forced to idle state. (reset state)|
|:::|1| OC and OCN outputs are enabled if their respective enable bits are set (CCxE, CCxNE in TIMx_CCER register).|

===== Programming Example =====

The code snippet below shows how to configure and use a GPIO pin as input.

<code c>
#include "reg_stm32f4xx.h"

RCC->AHBENR[0] |= (0x1 << 0u);          /* Enable GPIOA clock */
RCC->APBENR[0] |= (0x1 << 0u);          /* Enable TIM2 clock */

/* configure output */
GPIOA->MODER |= (0x2 << 0u);          /* Set pin 0 to Alternate Function */
GPIOA->AFR[0] |= (0x1 << 0u);         /* Set pin 0 to AF1 (TIM2) */
 
/* configure basic timer */
TIM2->PSC = 84000u - 1u;              /* Counting with f = 84MHz / 84000 = 1MHz */
TIM2->ARR = 512u;                     /* Count to 512 */

/* configure timer output */
TIM2->CCMR1 |= (0x6 << 4u);           /* Enable PWM mode 1 on channel 1 */
TIM2->CCER |= (0x1 << 0u);            /* Enable output on channel 1 */
 
TIM2->CR1 |= (0x1 << 0u);             /* Start timer */
</code>
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