ST STM8S Reference Manual

Auto-wakeup (AWU) RM0016
116/449 Doc ID 14587 Rev 8
12.3.2 Time base selection
Please refer to the Asynchronous prescaler register (AWU_APR) and Timebase selection
register (AWU_TBR) descriptions.
The AWU time intervals depend on the values of:
● AWUTB[3:0] bits. This gives the counter output rank.
● APR[5:0] bits. This gives the prescaler division factor (APR
DIV
).
15 non-overlapped ranges of time intervals can be defined as follows:
In order to obtain the right values for AWUTB[3:0] and APR
DIV
, you have to:
● First, search the interval range corresponding to the desired time interval. This gives
the AWUTB[3:0] value.
● Then APR
DIV
can be chosen to obtain a time interval value as close as possible to the
desired one. This can be done using the formulas listed in the table above.
Note: If the target value is between 2
11
x128/f
LS
and 2
11
x130/f
LS
or between 2
11
x320/f
LS
and
2
11
x330/f
LS
, the value closer to the target one must be chosen.
Table 25. Time base calculation table
Interval range
AWUTB[3:0]
APR
DIV
formula for
time interval
calculation
APR
DIV
range
f
LS
= f f
LS
= 128kHz
2/f - 64/f 0.015625 ms - 0.5 ms 0001 APR
DIV
/f
LS
2 to 64
2x32/f - 2x2x32/f 0.5 ms - 1.0 ms 0010 2 x APR
DIV
/f
LS
32 to 64
2x64/f - 2x2x64/f 1 ms - 2 ms 0011 2
2
x APR
DIV
/f
LS
32 to 64
2
2
x64/f - 2
2
x128/f 2 ms - 4ms 0100 2
3
x APR
DIV
/f
LS
32 to 64
2
3
x64/f - 2
3
x128/f 4 ms - 8 ms 0101 2
4
x APR
DIV
/f
LS
32 to 64
2
4
x64/f - 2
4
x128/f 8 ms - 16 ms 0110 2
5
x APR
DIV
/f
LS
32 to 64
2
5
x64/f - 2
5
x128/f 16 ms - 32 ms 0111 2
6
x APR
DIV
/f
LS
32 to 64
2
6
x64/f - 2
6
x128/f 32 ms - 64 ms 1000 2
7
x APR
DIV
/f
LS
32 to 64
2
7
x64/f - 2
7
x128/f 64 ms - 128 ms 1001 2
8
x APR
DIV
/f
LS
32 to 64
2
8
x64/f - 2
8
x128/f 128 ms - 256 ms 1010 2
9
x APR
DIV
/f
LS
32 to 64
2
9
x64/f - 2
9
x128/f 256 ms - 512 ms 1011 2
10
x APR
DIV
/f
LS
32 to 64
2
10
x64/f - 2
10
x128/f 512 ms - 1.024 s 1100 2
11
x APR
DIV
/f
LS
32 to 64
2
11
x64/f - 2
11
x128/f 1.024 s - 2.048 s 1101 2
12
x APR
DIV
/f
LS
32 to 64
2
11
x130/f - 2
11
x320/f 2.080 s - 5.120 s 1110 5 x 2
11
x APR
DIV
/f
LS
26 to 64
2
11
x330/f - 2
12
x960/f 5.280 s - 30.720s 1111 30 x 2
11
x APR
DIV
/f
LS
11 to 64

ST STM8S Specifications

General

Brand	ST
Model	STM8S
Category	Microcontrollers
Language	English