Line 42: Line 42:
 
1 = Transmit enabled<br>
 
1 = Transmit enabled<br>
 
0 = Transmit disabled
 
0 = Transmit disabled
Note: SREN/CREN overrides TXEN in Sync mode.
 
  
 
<b>SYNC:</b> USART Mode Select bit<br>
 
<b>SYNC:</b> USART Mode Select bit<br>
Line 50: Line 49:
 
<b>BRGH:</b> High Baud Rate Select bit<br>
 
<b>BRGH:</b> High Baud Rate Select bit<br>
 
1 = High speed<br>
 
1 = High speed<br>
0 = Low speed<br>
+
0 = Low speed
  
<b>TRMT:</b> Transmit Shift Register Status bit
+
<b>TRMT:</b> Transmit Shift Register Status bit<br>
 
1 = TSR empty<br>
 
1 = TSR empty<br>
0 = TSR full<br>
+
0 = TSR full
  
 
<b>TX9D:</b> 9th bit of Transmit Data, can be Parity bit
 
<b>TX9D:</b> 9th bit of Transmit Data, can be Parity bit

Revision as of 10:52, 5 May 2016

In this tutorial we are going to discuss the serial/UART communication using PIC16F877A.
PIC16F877A comes with inbuilt USART which can be used for Synchronous/Asynchronous communication. We will be discussing only the UART. After understating the basics of PIC16F877A UART module, We will see how to use the ExploreEmbedded libraries to communicate with any of the UART devices.

0 UART main.gif


UART Registers

The below table shows the registers associated with PIC16F877A UART.

Register Description
TXSTA Transmit Status And Control Register
RCSTA Receive Status And Control Register
SPBRG USART Baud Rate Generator




UART Register Configuration

Now lets see how to configure the individual registers for UART communication.

TXSTA
7 6 5 4 3 2 1 0
CSRC TX9 TXEN SYNC - BRGH TRMT TX9D

CSRC: Clock Source Select bit
Asynchronous mode:Don’t care.

TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission

TXEN: Transmit Enable bit
1 = Transmit enabled
0 = Transmit disabled

SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode

BRGH: High Baud Rate Select bit
1 = High speed
0 = Low speed

TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full

TX9D: 9th bit of Transmit Data, can be Parity bit


RCSTA
7 6 5 4 3 2 1 0
SPEN RX9 SREN CREN ADDEN FERR OERR RX9D

SPEN: Serial Port Enable bit
1 = Serial port enabled (configures RC7/RX/DT and RC6/TX/CK pins as serial port pins)
0 = Serial port disabled

RX9: 9-bit Receive Enable bit
1 = Selects 9-bit reception
0 = Selects 8-bit reception

SREN: Single Receive Enable bit
Asynchronous mode:Don’t care.

CREN: Continuous Receive Enable bit
Asynchronous mode:
1 = Enables continuous receive
0 = Disables continuous receive

ADDEN: Address Detect Enable bit
Asynchronous mode 9-bit (RX9 = 1):
1 = Enables address detection, enables interrupt and load of the receive buffer when RSR is set
0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit

FERR: Framing Error bit
1 = Framing error (can be updated by reading RCREG register and receive next valid byte)
0 = No framing error

OERR: Overrun Error bit
1 = Overrun error (can be cleared by clearing bit CREN)
0 = No overrun error

RX9D: 9th bit of Received Data (can be parity bit but must be calculated by user firmware)