RM0312 datasheet(129/275 Pages) STMICROELECTRONICS

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RM0312

16-bit general purpose timer (TIM2/TIM3)

170

Figure 49. 16-bit read sequence for the TIMx_CCRi register in capture mode

Figure 49 shows the sequence for reading the CCRi registers in the 16-bit timers. This

buffered value remains unchanged until the 16-bit read sequence is completed.

After a complete reading sequence, if only the TIMx_CCRiL register is read, it returns the

LS Byte of the count value at the time of the read.

If the MS byte is read after the LS byte, it no longer corresponds to the same captured value

as the LS byte.

17.5.1

Write sequence for 16-bit TIMx_CCRi registers

16-bit values are loaded in the TIMx_CCRi

registers through preload registers. This must

be performed by two write instructions, one for each byte. The MS byte must be written first.

The shadow register update is blocked as soon as the MS byte has been written, and stays

blocked until the LS byte has been written. Do not use the LDW instruction, as this writes

the LS byte first, and would produce wrong results in this case.

17.5.2

Input stage

Figure 50. Channel input stage block diagram

As shown in Figure 51, the input stage samples the corresponding TIi input to generate a

filtered signal TIiF. Then, an edge detector with polarity selection generates a signal (TIiFPx)

which can be used as trigger input by the clock/trigger controller or as the capture

command. It is prescaled before the capture register (ICiPS).

is frozen

Read

At t0

Read

Preload register

is no longer frozen

At t0 +

Δt

Other

instructions

Beginning of the sequence

Sequence completed

Preload register

LS Byte

MS Byte

is buffered into

shadow register

the preload register

Other

instructions

is buffered into

shadow register

the preload register

Other

instructions

IC1

IC2

Input Filter &

Edge Detector

TI1FP1

TRC

TI1FP2

TI2FP1

TI2FP2

TI1

TI2

XOR

TIMx_CH1

TIMx_CH2

to clock/trigger controller

TRC

TI1F_ED

to capture/compare channels

from Comparator

Input Filter &

Edge Detector

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