AT91SAM7X256B-AU Atmel, AT91SAM7X256B-AU Datasheet - Page 26

• Manufacturer Part Number: AT91SAM7X256B-AU
• Description: IC MCU 256KB FLASH 100LQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91SAM7X256B-AU

• Core Processor: ARM7
• Core Size: 16/32-Bit
• Speed: 55MHz
• Connectivity: CAN, Ethernet, I²C, SPI, SSC, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, DMA, POR, PWM, WDT
• Number Of I /o: 62
• Program Memory Size: 256KB (256K x 8)
• Program Memory Type: FLASH
• Ram Size: 64K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 100-LQFP
• Package: 100LQFP
• Device Core: ARM7TDMI
• Family Name: 91S
• Maximum Speed: 55 MHz
• Operating Supply Voltage: 1.8|3.3 V
• Data Bus Width: 32 Bit
• Number Of Programmable I/os: 62
• Interface Type: CAN/Ethernet/SPI/I2S/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Number Of Timers: 3
• Controller Family/series: AT91SAM7xxxxx
• No. Of I/o's: 62
• Ram Memory Size: 64KB
• Cpu Speed: 55MHz
• No. Of Timers: 1
• Rohs Compliant: Yes
• Cpu Family: 91S
• Device Core Size: 32b
• Frequency (max): 55MHz
• Total Internal Ram Size: 64KB
• # I/os (max): 62
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 1.8/3.3V
• Operating Supply Voltage (max): 1.95/3.6V
• Operating Supply Voltage (min): 1.65/3V
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 100
• Package Type: LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Compliant

9.1
9.1.1
26
Reset Controller
AT91SAM7X512/256/128 Preliminary
Brownout Detector and Power-on Reset
The AT91SAM7X512/256/128 embeds one brownout detection circuit and a power-on reset cell.
The power-on reset is supplied with and monitors VDDCORE.
Both signals are provided to the Flash to prevent any code corruption during power-up or power-
down sequences or if brownouts occur on the power supplies.
The power-on reset cell has a limited-accuracy threshold at around 1.5V. Its output remains low
during power-up until VDDCORE goes over this voltage level. This signal goes to the reset con-
troller and allows a full re-initialization of the device.
The brownout detector monitors the VDDCORE and VDDFLASH levels during operation by
comparing them to a fixed trigger level. It secures system operations in the most difficult environ-
ments and prevents code corruption in case of brownout on the VDDCORE or VDDFLASH.
When the brownout detector is enabled and VDDCORE decreases to a value below the trigger
level (Vbot18-, defined as Vbot18 - hyst/2), the brownout output is immediately activated.
When VDDCORE increases above the trigger level (Vbot18+, defined as Vbot18 + hyst/2), the
reset is released. The brownout detector only detects a drop if the voltage on VDDCORE stays
below the threshold voltage for longer than about 1µs.
The VDDCORE threshold voltage has a hysteresis of about 50 mV, to ensure spike free brown-
out detection. The typical value of the brownout detector threshold is 1.68V with an accuracy of
± 2% and is factory calibrated.
When the brownout detector is enabled and VDDFLASH decreases to a value below the trigger
level (Vbot33-, defined as Vbot33 - hyst/2), the brownout output is immediately activated.
When VDDFLASH increases above the trigger level (Vbot33+, defined as Vbot33 + hyst/2), the
reset is released. The brownout detector only detects a drop if the voltage on VDDCORE stays
below the threshold voltage for longer than about 1µs.
The VDDFLASH threshold voltage has a hysteresis of about 50 mV, to ensure spike free brown-
out detection. The typical value of the brownout detector threshold is 2.80V with an accuracy of
± 3.5% and is factory calibrated.
The brownout detector is low-power, as it consumes less than 28 µA static current. However, it
can be deactivated to save its static current. In this case, it consumes less than 1µA. The deac-
tivation is configured through the GPNVM bit 0 of the Flash.
• Based on one power-on reset cell and one brownout detector
• Status of the last reset, either Power-up Reset, Software Reset, User Reset, Watchdog
• Controls the internal resets and the NRST pin output
• Allows to shape a signal on the NRST line, guaranteeing that the length of the pulse meets
Reset, Brownout Reset
any requirement.
6120FS–ATARM–17-Feb-09