Receiver
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
20-11
20.2.1 Character Reception
During a UART reception, the receive shift register shifts a frame in through
URXD
. The SCI data
register is the read-only buffer between the MBus and the receive shift register. After a complete
frame shifts into the receive shift register, the data portion of the frame (the character) is
transferred to the SCI data register. The receive data register full flag, RDRF, in SCISR is set,
indicating that the received character can be read.
The overrun flag, OR, is set when software fails to read the SCIDR before the receive shift
register receives the next character. If the receive interrupt enable bit (SCICR[RIE]) is also set,
the Receive Data Register Full (RDRF) or the OR flags generate an interrupt request.
Begin an SCI reception as follows:
1.
Configure the SCI:
f. Select the target baud rate and write the appropriate value to the SCI Baud Rate
Register (SCIBR). Note that the baud-rate generator is disabled when the baud rate is
zero. Writing to 5 MSB bits of SCIBR (SBR[12–8]) has no effect without also writing
to 7 LSB of SCIBR (SBR[7–0]).
g. Configure
GPIO20
for UART
URXD
(see
— Select the UART
URXD
signal as the external connection via the GPIO port 20
configuration registers.
— Clear the direction bit for GPIO20 in the direction register to select input.
h. Write to the SCICR to configure data length, parity, and other configuration bits (LOOPS,
RSRC, M, WAKE, ILT, PE, PT) and enable the transmitter, interrupts, receive, and wake up
as required (TIE, TCIE, RIE, ILIE, TE, RE, RWU, and SBK).If the SBK bit is set, the receiver
wakes up if there are particular conditions on the
URXD
signal according to the WAKE control
bit. Refer to Section 21.2.7, Receiver Wake-Up.
2.
Perform the reception procedure for each character:
i. Poll the RDRF flag by reading the SCISR or responding to the UART interrupt.
j.
If the RDRF flag is set, read the data to be received from SCIDR, where the ninth bit is read
from R8 bit in SCIDR if the SCI is in 9-bit data format. Reading RDRF bit at SCISR and then
reading new data from SCIDR clears RDRF flag.
3.
Repeat step 2 for each subsequent reception.
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...