MPC8280 datasheet(721/1386 Pages) FREESCALE

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SCC UART Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

21-15

21.17 SCC UART Receive Buffer Descriptor (RxBD)

The CPM uses RxBDs to report on each buffer received. The CPM closes the current buffer, generates a

maskable interrupt, and starts receiving data into the next buffer after one of the following occurs:

•

A user-defined control character is received.

•

An error occurs during message processing.

•

A full receive buffer is detected.

•

A MAX_IDL number of consecutive idle characters is received.

•An ENTER HUNT MODE or CLOSE RXBD command is issued.

•

An address character is received in multidrop mode. The address character is written to the next

buffer for a software comparison.

Figure 21-7 shows an example of how RxBDs are used in receiving.

—

Reserved, should be cleared.

PEN

Parity enable.

0No parity.

1 Parity is enabled and determined by the parity mode bits.

12–13,

14–15

RPM,

TPM

Receiver/transmitter parity mode. Selects the type of parity check the receiver/transmitter performs;

can be modified on-the-fly. Receive parity errors can be ignored but not disabled.

00 Odd parity. If a transmitter counts an even number of ones in the data word, it sets the parity bit

so an odd number is sent. If a receiver receives an even number, a parity error is reported.

01 Low parity (space parity). A transmitter sends a zero in the parity bit position. If a receiver does

not read a 0 in the parity bit, a parity error is reported.

10 Even parity. Like odd parity, the transmitter adjusts the parity bit, as necessary, to ensure that

the receiver receives an even number of one bits; otherwise, a parity error is reported.

11 High parity (mark parity). The transmitter sends a one in the parity bit position. If the receiver

does not read a 1 in the parity bit, a parity error is reported.

Table 21-9. PSMR UART Field Descriptions (continued)

Bit

Name

Description

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