STMicroelectronics STM32F407 User Manual

DocID018909 Rev 11 981/1731
RM0090 Universal synchronous asynchronous receiver transmitter (USART)
1010
30.3.5 USART receiver tolerance to clock deviation
The USART asynchronous receiver works correctly only if the total clock system deviation is
smaller than the USART receiver’s tolerance. The causes which contribute to the total
deviation are:
• DTRA: Deviation due to the transmitter error (which also includes the deviation of the
transmitter’s local oscillator)
• DQUANT: Error due to the baud rate quantization of the receiver
• DREC: Deviation of the receiver’s local oscillator
• DTCL: Deviation due to the transmission line (generally due to the transceivers which
can introduce an asymmetry between the low-to-high transition timing and the high-to-
low transition timing)
DTRA + DQUANT + DREC + DTCL < USART receiver’s tolerance
9. 460.8 KBps 461.538 KBps 11.375 0.16 461.538 KBps 22.75 0.16
10. 921.6 KBps 913.043 KBps 5.75 0.93 923.076 KBps 11.375 0.93
11. 1.792 MBps 1.826 MBps 2.875 1.9 1.787Mbps 5.875 0.27
12. 1.8432 MBps 1.826 MBps 2.875 0.93 1.826 MBps 5.75 0.93
13. 3.584 MBps 3.5 MBps 1.5 2.34 3.652 MBps 2.875 1.9
14. 3.6864 MBps 3.82 MBps 1.375 3.57 3.652 MBps 2.875 0.93
15. 7.168 MBps N.A N.A N.A 7 MBps 1.5 2.34
16. 7.3728 MBps N.A N.A N.A 7.636 MBps 1.375 3.57
18. 9 MBps N.A N.A N.A 9.333 MBps 1.125 3.7
20. 10.5 MBps N.A N.A N.A 10.5 MBps 1 0
1. The lower the CPU clock the lower the accuracy for a particular baud rate. The upper limit of the achievable baud rate can
be fixed with these data.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.
Table 142. Error calculation for programmed baud rates at f
PCLK
= 42 MHz or f
PCLK
= 84 MHz,
oversampling by 8
(1)(2)
(continued)
Oversampling by 8 (OVER8=1)
Baud rate f
PCLK
= 42 MHz f
PCLK
= 84 MHz
S.No Desired Actual
Value
programme
d in the
baud rate
register
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
Actual
Value
programmed
in the baud
rate register
%
Error

STMicroelectronics STM32F407 Specifications

General

Brand	STMicroelectronics
Model	STM32F407
Category	Controller
Language	English