ST STM8S Reference Manual

16-bit advanced control timer (TIM1) RM0016
164/449 Doc ID 14587 Rev 8
The capture/compare block is made of one preload register and one shadow register. Write
and read always access the preload register. In capture mode, captures are made in the
shadow register, which is copied into the preload register. In compare mode, the content of
the preload register is copied into the shadow register which is compared to the counter.
When the channel is configured in output mode (CCiS = 00 in the TIM1_CCMRi registers),
the TIM1_CCRi registers can be accessed without any restriction.
When the channel is configured in input mode, the sequence for reading the TIM1_CCRi
registers is the same as for the counter (see Figure 62). When a capture occurs, the content
of the counter is captured into the TIM1_CCRi shadow registers. Then this value is loaded
into the preload register, except during a read sequence, when the preload register is
frozen.
Figure 62. 16-bit read sequence for the TIM1_CCRi register in capture mode
Figure 62 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 read sequence, if only the TIM1_CCRiL registers are read, they return 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 TIM1_CCRi registers
16-bit values are loaded in the TIM1_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 is written. Do not use the LDW instruction, as this writes the LS
byte first, and produces incorrect results in this case.
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

ST STM8S Specifications

General

Brand	ST
Model	STM8S
Category	Microcontrollers
Language	English