MPC8280 datasheet(718/1386 Pages) FREESCALE

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SCC UART Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

21-12

Freescale Semiconductor

21.15 Handling Errors in the SCC UART Controller

The UART controller reports character reception and transmission error conditions via the BDs, the error

counters, and the SCCE. Modem interface lines can be monitored by the port C pins. Transmission errors

are described in Table 21-7.

Reception errors are described in Table 21-8.

Table 21-7. Transmission Errors

Error

Description

CTS Lost

during

Character

Transmission

When CTS negates during transmission, the channel stops after finishing the current character. The

CP sets TxBD[CT] and generates the TX interrupt if it is not masked. The channel resumes

transmission after the RESTART TRANSMIT command is issued and CTS is asserted.

Note that if CTS is used, the UART also offers an asynchronous flow control option that does not

generate an error. See the description of PSMR[FLC] in Table 21-9.

Table 21-8. Reception Errors

Error

Description

Overrun

Occurs when the channel overwrites the previous character in the Rx FIFO with a new character, losing

the previous character. The channel then writes the new character to the buffer, closes it, sets

RxBD[OV], and generates an RX interrupt if not masked. In automatic multidrop mode, the receiver

enters hunt mode immediately.

CD Lost

during

Character

Reception

If this error occurs and the channel is using this pin to automatically control reception, the channel

terminates character reception, closes the buffer, sets RxBD[CD], and generates the RX interrupt if not

masked. This error has the highest priority. The last character in the buffer is lost and other errors are

not checked. In automatic multidrop mode, the receiver enters the hunt mode immediately.

Parity

When a parity error occurs, the channel writes the received character to the buffer, closes the buffer,

sets RxBD[PR], and generates the RX interrupt if not masked. The channel also increments the parity

error counter PAREC. In automatic multidrop mode, the receiver enters hunt mode immediately.

Noise

A noise error occurs when the three samples of a bit are not identical. When this error occurs, the

channel writes the received character to the buffer, proceeds normally, but increments the noise error

counter NOSEC. Note that this error does not occur in synchronous mode.

Idle

Sequence

Receive

If the UART is receiving data and gets an idle character (all ones), the channel begins counting

consecutive idle characters received. If MAX_IDL is reached, the buffer is closed and an RX interrupt

is generated if not masked. If no buffer is open, this event does not generate an interrupt or any status

information. The internal idle counter (IDLC) is reset every time a character is received. To disable the

idle sequence function, clear MAX_IDL.

MPC8280 Datasheet(PDF) 718 Page - Freescale Semiconductor, Inc

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