Communication Interfaces; Table 60. Iwdg Min/Max Timeout Period At 40 Khz (Lsi); Table 61. Wwdg Min/Max Timeout Value At 48 Mhz (Pclk) - STMicroelectronics STM32F042G4 Manual

Electrical characteristics
Symbol
t
MAX_COUNT
Prescaler divider
/16
/32
/64
/128
/256
1. These timings are given for a 40 kHz clock but the microcontroller internal RC frequency can vary from 30
to 60 kHz. Moreover, given an exact RC oscillator frequency, the exact timings still depend on the phasing
of the APB interface clock versus the LSI clock so that there is always a full RC period of uncertainty.
Prescaler
1
2
4
8
6.3.20

Communication interfaces

2
I C interface characteristics
The I2C interface meets the timings requirements of the I
manual rev. 03 for:

Standard-mode (Sm): with a bit rate up to 100 kbit/s

Fast-mode (Fm): with a bit rate up to 400 kbit/s

Fast-mode Plus (Fm+): with a bit rate up to 1 Mbit/s.
The I2C timings requirements are guaranteed by design when the I2C peripheral is properly
configured (refer to Reference manual).
The SDA and SCL I/O requirements are met with the following restrictions: the SDA and
SCL I/O pins are not "true" open-drain. When configured as open-drain, the PMOS
connected between the I/O pin and V
support Fm+ low level output current maximum requirement. Refer to
port characteristics
88/117
Table 59. TIMx characteristics (continued)
Parameter
Maximum possible count
with 32-bit counter

Table 60. IWDG min/max timeout period at 40 kHz (LSI)

PR[2:0] bits
/4 0
/8 1
2
3
4
5
6 or 7

Table 61. WWDG min/max timeout value at 48 MHz (PCLK)

WDGTB
0
1
2
3
for the I2C I/Os characteristics.
Conditions
f = 48 MHz
TIMxCLK
Min timeout RL[11:0]=
0x000
0.1
0.2
0.4
0.8
1.6
3.2
6.4
Min timeout value
0.0853
0.1706
0.3413
0.6826
is disabled, but is still present. Only FTf I/O pins
DDIOx
DocID025832 Rev 2
STM32F042xx
Min Max
- 65536 × 65536
- 89.48
(1)
Max timeout RL[11:0]=
0xFFF
409.6
819.2
1638.4
3276.8
6553.6
13107.2
26214.4
Max timeout value
5.4613
10.9226
21.8453
43.6906
2
C-bus specification and user
Section 6.3.14: I/O
Unit
t
TIMxCLK
s
Unit
ms
Unit
ms