SAM7SE256 Atmel Corporation, SAM7SE256 Datasheet - Page 168
SAM7SE256
Manufacturer Part Number
SAM7SE256
Description
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
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22.6.3
22.6.3.1
22.6.3.2
168
SAM7SE512/256/32
Read Access
Read Protocols
Standard Read Protocol
Figure 22-10. Write Access with 1 Wait State
The SMC provides two alternative protocols for external memory read accesses: standard and
early read. The difference between the two protocols lies in the behavior of the NRD signal.
For write accesses, in both protocols, NWE has the same behavior. In the second half of the
master clock cycle, NWE always goes low (see
The protocol is selected by the DRP field in SMC_CSR
page
Note:
Standard read protocol implements a read cycle during which NRD and NWE are similar. Both
are active during the second half of the clock cycle. The first half of the clock cycle allows time to
ensure completion of the previous access as well as the output of address lines and NCS before
the read cycle begins.
During a standard read protocol, NCS is set low and address lines are valid at the beginning of
the external memory access, while NRD goes low only in the second half of the master clock
cycle to avoid bus conflict. See
196.). Standard read protocol is the default protocol after reset.
In the following waveforms and descriptions NWE represents NWE, NWR0 and NWR1 unless
NWR0 and NWR1 are otherwise represented. In addition, NCS represents NCS[7:0] (see
“I/O Lines” on page
D[15:0]
A[22:0]
NWE
MCK
NCS
163,
Table 22-1
Figure
22-11.
and
Table
Figure 22-18 on page
22-2).
(See “SMC Chip Select Registers” on
173).
6222F–ATARM–14-Jan-11
22.5.1
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