mcf5282 Freescale Semiconductor, Inc, mcf5282 Datasheet - Page 441

• Manufacturer Part Number: mcf5282
• Manufacturer: Freescale Semiconductor, Inc

framing error, overrun error, and received break conditions set the respective PE, FE, OE, and RB error
and break flags in the USRn at the received character boundary. They are valid only if USRn[RXRDY] is
set.
If a break condition is detected (URXDn is low for the entire character including the stop bit), a character
of all 0s loads into the receiver holding register and USRn[RB,RXRDY] are set. URXDn must return to a
high condition for at least one-half bit time before a search for the next start bit begins.
The receiver detects the beginning of a break in the middle of a character if the break persists through the
next character time. The receiver places the damaged character in the Rx FIFO and sets the corresponding
USRn error bits and USRn[RXRDY]. Then, if the break lasts until the next character time, the receiver
places an all-zero character into the Rx FIFO and sets USRn[RB,RXRDY].
Figure 23-20
23.4.2.3
The FIFO is used in the UART’s receive buffer logic. The FIFO consists of three receiver holding registers.
The receive buffer consists of the FIFO and a receiver shift register connected to the URXDn (see
Figure
holding register position of the FIFO. Therefore, data flowing from the receiver to the CPU is
quadruple-buffered.
In addition to the data byte, three status bits—parity error (PE), framing error (FE), and received break
(RB)—are appended to each data character in the FIFO; overrun error (OE) is not appended. By
Freescale Semiconductor
USRn[RXRDY]
USRn[FFULL]
23-18). Data is assembled in the receiver shift register and loaded into the top empty receiver
USRn[OE]
URXDn
URTSn
1
Receiver
Enabled
Overrun
Internal
UMR2n[RXRTS] = 1
module
select
FIFO
shows receiver functional timing.
1
UOP0[RTS] = 1
Manually asserted first time,
automatically negated if overrun occurs
C1
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Status
(C1)
Data
Figure 23-20. Receiver Timing Diagram
C2
C3
C4
C5 is
lost
C5
Status
Data
(C2)
C6
Automatically asserted
when ready to receive
Status
(C3)
Data
C6, C7, and C8 is lost
Status
Data
(C4)
C7
command
Reset by
UART Modules
C8
23-21