SAM7SE256 Atmel Corporation, SAM7SE256 Datasheet - Page 169

• 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

22.6.3.3
22.6.4
6222F–ATARM–14-Jan-11
Wait State Management
Early Read Protocol
Figure 22-11. Standard Read Protocol
Early read protocol provides more time for a read access from the memory by asserting NRD at
the beginning of the clock cycle. In the case of successive read cycles in the same memory,
NRD remains active continuously. Since a read cycle normally limits the speed of operation of
the external memory system, early read protocol can allow a faster clock frequency to be used.
However, an extra wait state is required in some cases to avoid contentions on the external bus.
Figure 22-12. Early Read Protocol
The SMC can automatically insert wait states. The different types of wait states managed are
listed below:
• Standard wait states
• External wait states
• Data float wait states
• Chip select change wait states
• Early Read wait states
D[15:0]
A[22:0]
D[15:0]
A[22:0]
MCK
NRD
NCS
MCK
NRD
NCS
SAM7SE512/256/32
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