807
11054A–ATARM–27-Jul-11
SAM9X25
807
11054A–ATARM–27-Jul-11
SAM9X25
39.7.3
Synchronous and Asynchronous Modes
39.7.3.1
Transmitter Operations
The transmitter performs the same in both synchronous and asynchronous operating modes
(SYNC = 0 or SYNC = 1). One start bit, up to 9 data bits, one optional parity bit and up to two
stop bits are successively shifted out on the TXD pin at each falling edge of the programmed
serial clock.
The number of data bits is selected by the CHRL field and the MODE 9 bit in the Mode Register
(US_MR). Nine bits are selected by setting the MODE 9 bit regardless of the CHRL field. The
parity bit is set according to the PAR field in US_MR. The even, odd, space, marked or none
parity bit can be configured. The MSBF field in US_MR configures which data bit is sent first. If
written to 1, the most significant bit is sent first. If written to 0, the less significant bit is sent first.
The number of stop bits is selected by the NBSTOP field in US_MR. The 1.5 stop bit is sup-
ported in asynchronous mode only.
Figure 39-6.
Character Transmit
The characters are sent by writing in the Transmit Holding Register (US_THR). The transmitter
reports two status bits in the Channel Status Register (US_CSR): TXRDY (Transmitter Ready),
which indicates that US_THR is empty and TXEMPTY, which indicates that all the characters
written in US_THR have been processed. When the current character processing is completed,
the last character written in US_THR is transferred into the Shift Register of the transmitter and
US_THR becomes empty, thus TXRDY rises.
Both TXRDY and TXEMPTY bits are low when the transmitter is disabled. Writing a character in
US_THR while TXRDY is low has no effect and the written character is lost.
Figure 39-7.
Transmitter Status
D0
D1
D2
D3
D4
D5
D6
D7
TXD
Start
Bit
Parity
Bit
Stop
Bit
Example: 8-bit, Parity Enabled One Stop
Baud Rate
Clock
D0
D1
D2
D3
D4
D5
D6
D7
TXD
Start
Bit
Parity
Bit
Stop
Bit
Baud Rate
Clock
Start
Bit
Write
US_THR
D0
D1
D2
D3
D4
D5
D6
D7
Parity
Bit
Stop
Bit
TXRDY
TXEMPTY
Содержание SAM9X25
Страница 26: ...26 11054A ATARM 27 Jul 11 SAM9X25...
Страница 138: ...138 11054A ATARM 27 Jul 11 SAM9X25 138 11054A ATARM 27 Jul 11 SAM9X25...
Страница 162: ...162 11054A ATARM 27 Jul 11 SAM9X25 162 11054A ATARM 27 Jul 11 SAM9X25...
Страница 216: ...216 11054A ATARM 27 Jul 11 SAM9X25 216 11054A ATARM 27 Jul 11 SAM9X25...
Страница 266: ...266 11054A ATARM 27 Jul 11 SAM9X25 266 11054A ATARM 27 Jul 11 SAM9X25...
Страница 330: ...330 11054A ATARM 27 Jul 11 SAM9X25 330 11054A ATARM 27 Jul 11 SAM9X25...
Страница 374: ...374 11054A ATARM 27 Jul 11 SAM9X25...
Страница 468: ...468 11054A ATARM 27 Jul 11 SAM9X25 468 11054A ATARM 27 Jul 11 SAM9X25...
Страница 532: ...532 11054A ATARM 27 Jul 11 SAM9X25 532 11054A ATARM 27 Jul 11 SAM9X25...
Страница 692: ...692 11054A ATARM 27 Jul 11 SAM9X25 692 11054A ATARM 27 Jul 11 SAM9X25...
Страница 777: ...777 11054A ATARM 27 Jul 11 SAM9X25 777 11054A ATARM 27 Jul 11 SAM9X25...
Страница 886: ...886 11054A ATARM 27 Jul 11 SAM9X25 886 11054A ATARM 27 Jul 11 SAM9X25...
Страница 962: ...962 11054A ATARM 27 Jul 11 SAM9X25 962 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1036: ...1036 11054A ATARM 27 Jul 11 SAM9X25 1036 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1067: ...1067 11054A ATARM 27 Jul 11 SAM9X25 1067 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Enable pause time zero interrupt...
Страница 1069: ...1069 11054A ATARM 27 Jul 11 SAM9X25 1069 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Disable pause time zero interrupt...
Страница 1071: ...1071 11054A ATARM 27 Jul 11 SAM9X25 1071 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Pause time zero interrupt masked...
Страница 1128: ...1128 11054A ATARM 27 Jul 11 SAM9X25 1128 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1130: ...1130 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1131: ...1131 11054A ATARM 27 Jul 11 SAM9X25 Revision History Doc Rev 11054A Comments Change Request Ref 1st issue...
Страница 1132: ...1132 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1144: ...xii 11054A ATARM 27 Jul 11 SAM9X25...