SAM7SE256 Atmel Corporation, SAM7SE256 Datasheet - Page 208

• Manufacturer Part Number: SAM7SE256
• Manufacturer: Atmel Corporation

Specifications of SAM7SE256

• Flash (kbytes): 256 Kbytes
• Pin Count: 144
• Max. Operating Frequency: 48 MHz
• Cpu: ARM7TDMI
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 88
• Ext Interrupts: 88
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 3
• Ssc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 384
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 32
• Self Program Memory: NO
• External Bus Interface: 1
• Dram Memory: sdram
• Nand Interface: Yes
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8/3.3
• Operating Voltage (vcc): 3.0 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 3
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: No

23.6.5
23.6.5.1
Figure 23-7. Self-refresh Mode Behavior
208
SDRAMC_SRR
SDCKE
A[12:0]
SDWE
SDCK
SDCS
Write
RAS
CAS
SAM7SE512/256/32
Power Management
Self-refresh Mode
SRCB = 1
Self-refresh mode is used in power-down mode, i.e., when no access to the SDRAM device is
possible. In this case, power consumption is very low. The mode is activated by programming
the self-refresh command bit (SRCB) in SDRAMC_SRR. In self-refresh mode, the SDRAM
device retains data without external clocking and provides its own internal clocking, thus per-
forming its own auto-refresh cycles. All the inputs to the SDRAM device become “don’t care”
except SDCKE, which remains low. As soon as the SDRAM device is selected, the SDRAM
Controller provides a sequence of commands and exits self-refresh mode, so the self-refresh
command bit is disabled.
To re-activate this mode, the self-refresh command bit must be re-programmed.
The SDRAM device must remain in self-refresh mode for a minimum period of t
remain in self-refresh mode for an indefinite period. This is described in
Self Refresh Mode
to the SDRAM Controller
Access Request
T
Figure 23-7
XSR
= 3
6222F–ATARM–14-Jan-11
RAS
below.
Row
and may