Datasheet

PIC16(L)F1526/7
DS41458C-page 262  2011-2013 Microchip Technology Inc.
22.1.2.8 Asynchronous Reception Set-up:
1. Initialize the SPxBRGH:SPxBRGL register pair
and the BRGH and BRG16 bits to achieve the
desired baud rate (see
Section 22.4 “EUSART
Baud Rate Generator (BRG)”
).
2. Set the RXx/DTx and TXx/CKx TRIS controls to
‘1’.
3. Enable the serial port by setting the SPEN bit
and the RXx/DTx pin TRIS bit. The SYNC bit
must be clear for asynchronous operation.
4. If interrupts are desired, set the RCxIE interrupt
enable bit and set the GIE and PEIE bits of the
INTCON register.
5. If 9-bit reception is desired, set the RX9 bit.
6. Enable reception by setting the CREN bit.
7. The RCxIF interrupt flag bit will be set when a
character is transferred from the RSR to the
receive buffer. An interrupt will be generated if
the RCxIE interrupt enable bit was also set.
8. Read the RCxSTA register to get the error flags
and, if 9-bit data reception is enabled, the ninth
data bit.
9. Get the received 8 Least Significant data bits
from the receive buffer by reading the RCxREG
register.
10. If an overrun occurred, clear the OERR flag by
clearing the CREN receiver enable bit.
22.1.2.9 9-bit Address Detection Mode Set-up
This mode would typically be used in RS-485 systems.
To set up an Asynchronous Reception with Address
Detect Enable:
1. Initialize the SPxBRGH, SPxBRGL register pair
and the BRGH and BRG16 bits to achieve the
desired baud rate (see
Section 22.4 “EUSART
Baud Rate Generator (BRG)”
).
2. Set the RXx/DTx and TXx/CKx TRIS controls to
‘1’.
3. Enable the serial port by setting the SPEN bit.
The SYNC bit must be clear for asynchronous
operation.
4. If interrupts are desired, set the RCxIE interrupt
enable bit and set the GIE and PEIE bits of the
INTCON register.
5. Enable 9-bit reception by setting the RX9 bit.
6. Enable address detection by setting the ADDEN
bit.
7. Enable reception by setting the CREN bit.
8. The RCxIF interrupt flag bit will be set when a
character with the ninth bit set is transferred
from the RSR to the receive buffer. An interrupt
will be generated if the RCxIE interrupt enable
bit was also set.
9. Read the RCxSTA register to get the error flags.
The ninth data bit will always be set.
10. Get the received 8 Least Significant data bits
from the receive buffer by reading the RCxREG
register. Software determines if this is the
device’s address.
11. If an overrun occurred, clear the OERR flag by
clearing the CREN receiver enable bit.
12. If the device has been addressed, clear the
ADDEN bit to allow all received data into the
receive buffer and generate interrupts.
FIGURE 22-5: ASYNCHRONOUS RECEPTION
Start
bit
bit 7/8
bit 1bit 0
bit 7/8
bit 0Stop
bit
Start
bit
Start
bit
bit 7/8
Stop
bit
RXx/DTx pin
Reg
Rcv Buffer Reg
Rcv Shift
Read Rcv
Buffer Reg
RCxREG
RCxIF
(Interrupt Flag)
OERR bit
CREN
Word 1
RCxREG
Word 2
RCxREG
Stop
bit
Note: This timing diagram shows three words appearing on the RXx/DTx input. The RCxREG (receive buffer) is read after the third
word, causing the OERR (overrun) bit to be set.
RCIDL