为什么pic16f1947在帧的末尾有帧错误？

嗨，我使用pic16F1947和波特率38400的UART，DPS是8N1。为了配置串行端口，我们使用BRGH=1；//BRGH=1BRG16=1；//BRG16=0SPBRGH=0x00；//设置波特率38400SPBRGL=0xCF；//设置波特率38400CREN=1；//SYNC=0；//异步SPEN=1；//验证串行PORTTX9＝0；// 8位TX9D＝0；//TrMT＝1；//RX9＝0；//RX9D＝0；//RCIE＝0；出于某种原因，观察波特率为38700（为什么？）而不是38400，但没关系，因为它在误差范围之内。通常，在38700波特率的情况下，对于配置在38400：波特率38400=>；大小比特：2604166666666667e-6=>；1比特停止比特是：9*size=234375us，停止在10*size=260.416uSbaudrate 38700大小比特=>；2583979328165375e-6=>1比特。从2325558us到258.397，通常位的逻辑状态取在位的中间。所以，为什么我的示波器ktronixmdo4054b-3（它是一个好的示波器）告诉我在帧的末尾有帧错误？…



      以下为原文

    Hi,

I'm using the pic16F1947 and the UART at the baudrate 38400 and the DPS is 8N1.

to configure the serial port we use that :

BRGH = 1; // BRGH à 1
BRG16 = 1; // BRG16 à 0
SPBRGH = 0x00; // set baud rate to 38400
SPBRGL = 0xCF; // set baud rate to 38400
CREN = 1; //
SYNC = 0; // asynchrone
SPEN = 1; // validate serial port
TX9 = 0; // 8 bit
TX9D = 0; //

TRMT = 1; //
RX9 = 0; //
RX9D = 0; //
RCIE = 0; //

is it correct ?

for some reason the observe baudrate is 38700 ( why ?)  and not 38400, but it's ok because it's within the margin error. Normally with a baudrate at 38700 the bit stop is detected correctly for a receiver configured at 38400:


baudrate 38400 => size bit  : 26,04166666666667e-6  => 1 bit stop bit is at : 9*size= 234,375 us and stop at 10*size= 260.416uS
baudrate 38700 size bit => 25,83979328165375e-6 => 1 bit     from 232,558 us to  258.397us

normally the logic state of the bit is taken in the middle of the bit.


So, why my oscillosope tektronix mdo4054b-3 ( it is a good one) tell that I've framing error at end of the frame ? ....