AT91SAM7S256D-AU Atmel, AT91SAM7S256D-AU Datasheet - Page 386

• Manufacturer Part Number: AT91SAM7S256D-AU
• Description: ARM Microcontrollers - MCU 256K Flash SRAM 64K ARM based MCU
• Manufacturer: Atmel
• Series: SAM7S256r

Specifications of AT91SAM7S256D-AU

• Rohs: yes
• Core: ARM
• Processor Series: AT91SAM
• Data Bus Width: 16 bit/32 bit
• Maximum Clock Frequency: 55 MHz
• Program Memory Size: 256 KB
• Data Ram Size: 64 KB
• On-chip Adc: Yes
• Operating Supply Voltage: 3 V to 3.6 V
• Operating Temperature Range: - 40 C to + 85 C
• Package / Case: LQFP-64
• Mounting Style: SMD/SMT
• Interface Type: 2-Wire, I2S, SPI, USART
• Length: 7 mm

31.6.7
31.6.8
31.6.8.1
The USART features modem mode, which enables control of the signals: DTR (Data Terminal Ready), DSR (Data
Set Ready), RTS (Request to Send), CTS (Clear to Send), DCD (Data Carrier Detect) and RI (Ring Indicator).
While operating in modem mode, the USART behaves as a DTE (Data Terminal Equipment) as it drives DTR and
RTS and can detect level change on DSR, DCD, CTS and RI.
Setting the USART in modem mode is performed by writing the USART_MODE field in the Mode Register
(US_MR) to the value 0x3. While operating in modem mode the USART behaves as though in asynchronous mode
and all the parameter configurations are available.
Table 31-11
Table 31-11. Circuit References
The control of the DTR output pin is performed by writing the Control Register (US_CR) with the DTRDIS and
DTREN bits respectively at 1. The disable command forces the corresponding pin to its inactive level, i.e. high. The
enable command forces the corresponding pin to its active level, i.e. low. RTS output pin is automatically controlled
in this mode
The level changes are detected on the RI, DSR, DCD and CTS pins. If an input change is detected, the RIIC,
DSRIC, DCDIC and CTSIC bits in the Channel Status Register (US_CSR) are set respectively and can trigger an
interrupt. The status is automatically cleared when US_CSR is read. Furthermore, the CTS automatically disables
the transmitter when it is detected at its inactive state. If a character is being transmitted when the CTS rises, the
character transmission is completed before the transmitter is actually disabled.
The USART can be programmed to operate in three different test modes. The internal loopback capability allows
on-board diagnostics. In the loopback mode the USART interface pins are disconnected or not and reconfigured
for loopback internally or externally.
Normal mode connects the RXD pin on the receiver input and the transmitter output on the TXD pin.
Figure 31-30. Normal Mode Configuration
USART Pin
TXD
RTS
DTR
RXD
CTS
DSR
DCD
RI
SAM7S512/256/128/64/321/161 Modem Mode
Test Modes
Normal Mode
gives the correspondence of the USART signals with modem connection standards.
V24
2
4
20
3
5
6
8
22
Transmitter
CCITT
103
105
108.2
104
106
107
109
125
Receiver
Direction
From terminal to modem
From terminal to modem
From modem to terminal
From terminal to modem
From terminal to modem
From terminal to modem
From terminal to modem
From terminal to modem
RXD
TXD
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
386