AT91RM9200-QI-002 Atmel, AT91RM9200-QI-002 Datasheet - Page 424

• Manufacturer Part Number: AT91RM9200-QI-002
• Description: IC ARM9 MCU 208 PQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91RM9200-QI-002

• Core Processor: ARM9
• Core Size: 16/32-Bit
• Speed: 180MHz
• Connectivity: EBI/EMI, Ethernet, I²C, MMC, SPI, SSC, UART/USART, USB
• Peripherals: POR
• Number Of I /o: 122
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: ROM
• Ram Size: 48K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 208-MQFP, 208-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

30.6.3.7
Figure 30-12. Timeguard Operations
424
Baud Rate
TXEMPTY
US_THR
TXRDY
Clock
Write
TXD
AT91RM9200
Transmitter Timeguard
Start
Bit
D0
D1
The transmitter sends an address byte (parity bit set) when SENDA is written to US_CR. In this
case, the next byte written to US_THR is transmitted as an address. Any character written in
US_THR without having written the command SENDA is transmitted normally with the parity at
0.
The timeguard feature enables the USART interface with slow remote devices.
The timeguard function enables the transmitter to insert an idle state on the TXD line between
two characters. This idle state actually acts as a long stop bit.
The duration of the idle state is programmed in the TG field of the Transmitter Timeguard Regis-
ter (US_TTGR). When this field is programmed at zero no timeguard is generated. Otherwise,
the transmitter holds a high level on TXD after each transmitted byte during the number of bit
periods programmed in TG in addition to the number of stop bits.
As illustrated in
the programming of a timeguard. TXRDY rises only when the start bit of the next character is
sent, and thus remains at 0 during the timeguard transmission if a character has been written in
US_THR. TXEMPTY remains low until the timeguard transmission is completed as the time-
guard is part of the current character being transmitted.
Table 30-7
in relation to the function of the Baud Rate.
Table 30-7.
D2
D3
D4
D5
Baud Rate
indicates the maximum length of a timeguard period that the transmitter can handle
bit/sec
14400
19200
28800
33400
1 200
9 600
D6
Maximum Timeguard Length Depending on Baud Rate
Figure
D7
Parity
Bit
Stop
30-12, the behavior of TXRDY and TXEMPTY status bits is modified by
Bit
TG = 4
Start
Bit
D0
Bit time
69.4
52.1
34.7
29.9
104
833
µs
D1
D2
D3
D4
D5
D6
D7
Parity
Bit
Stop
Bit
Timeguard
212.50
26.56
17.71
13.28
8.85
7.63
ms
1768I–ATARM–09-Jul-09
TG = 4