COP8CCR9IMT7SLASHNOPB datasheet(63/111 Pages) TI1

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COP8CBR9, COP8CCR9, COP8CDR9

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SNOS535I – OCTOBER 2000 – REVISED MARCH 2013

5.13.5 FRAMING FORMATS

The USART supports several serial framing formats (Figure 5-17). The format is selected using control

bits in the ENU, ENUR and ENUI registers.

The first format (1, 1a, 1b, 1c) for data transmission (CHL0 = 1, CHL1 = 0) consists of Start bit, seven

Data bits (excluding parity) and one or two Stop bits. In applications using parity, the parity bit is

generated and verified by hardware.

The second format (CHL0 = 0, CHL1 = 0) consists of one Start bit, eight Data bits (excluding parity) and

7/8, one or two Stop bits. Parity bit is generated and verified by hardware.

The third format for transmission (CHL0 = 0, CHL1 = 1) consists of one Start bit, nine Data bits and one or

two Stop bits. This format also supports the USART “ATTENTION” feature. When operating in this format,

all eight bits of TBUF and RBUF are used for data. The ninth data bit is transmitted and received using

two bits in the ENU and ENUR registers, called XBIT9 and RBIT9. RBIT9 is a read only bit. Parity is not

generated or verified in this mode.

The parity is enabled/disabled by PEN bit located in the ENU register. Parity is selected for 7- and 8-bit

modes only. If parity is enabled (PEN = 1), the parity selection is then performed by PSEL0 and PSEL1

bits located in the ENU register.

Note that the XBIT9/PSEL0 bit located in the ENU register serves two mutually exclusive functions. This

bit programs the ninth bit for transmission when the USART is operating with nine data bits per frame.

There is no parity selection in this framing format. For other framing formats XBIT9 is not needed and the

bit is PSEL0 used in conjunction with PSEL1 to select parity.

The frame formats for the receiver differ from the transmitter in the number of Stop bits required. The

receiver only requires one Stop bit in a frame, regardless of the setting of the Stop bit selection bits in the

control register. Note that an implicit assumption is made for full duplex USART operation that the framing

formats are the same for the transmitter and receiver.

Functional Description

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