SAM9G20 Atmel Corporation, SAM9G20 Datasheet - Page 179
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SAM9G20
Manufacturer Part Number
SAM9G20
Description
Manufacturer
Atmel Corporation
Datasheets
1.SAM9261.pdf
(248 pages)
2.SAM9261.pdf
(1274 pages)
3.SAM9261.pdf
(43 pages)
4.SAM9G20.pdf
(42 pages)
5.SAM9G20.pdf
(832 pages)
Specifications of SAM9G20
Flash (kbytes)
0 Kbytes
Pin Count
217
Max. Operating Frequency
400 MHz
Cpu
ARM926
Hardware Qtouch Acquisition
No
Max I/o Pins
96
Ext Interrupts
96
Usb Transceiver
3
Usb Speed
Full Speed
Usb Interface
Host, Device
Spi
2
Twi (i2c)
1
Uart
7
Ssc
1
Ethernet
1
Sd / Emmc
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
Yes
Adc Channels
4
Adc Resolution (bits)
10
Adc Speed (ksps)
95
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)
0.9 to 1.1
Fpu
No
Mpu / Mmu
No/Yes
Timers
6
Output Compare Channels
6
Input Capture Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
No
- SAM9261 PDF datasheet
- SAM9261 PDF datasheet #2
- SAM9261 PDF datasheet #3
- SAM9G20 PDF datasheet #4
- SAM9G20 PDF datasheet #5
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- Download datasheet (13Mb)
21.10 Data Float Wait States
21.10.1
6384E–ATARM–05-Feb-10
READ_MODE
Some memory devices are slow to release the external bus. For such devices, it is necessary to
add wait states (data float wait states) after a read access:
The Data Float Output Time (t
TDF_CYCLES field of the SMC_MODE register for the corresponding chip select. The value of
TDF_CYCLES indicates the number of data float wait cycles (between 0 and 15) before the
external device releases the bus, and represents the time allowed for the data output to go to
high impedance after the memory is disabled.
Data float wait states do not delay internal memory accesses. Hence, a single access to an
external memory with long t
memory.
The data float wait states management depends on the READ_MODE and the TDF_MODE
fields of the SMC_MODE register for the corresponding chip select.
Setting the READ_MODE to 1 indicates to the SMC that the NRD signal is responsible for turn-
ing off the tri-state buffers of the external memory device. The Data Float Period then begins
after the rising edge of the NRD signal and lasts TDF_CYCLES MCK cycles.
When the read operation is controlled by the NCS signal (READ_MODE = 0), the TDF field gives
the number of MCK cycles during which the data bus remains busy after the rising edge of NCS.
Figure 21-21
assuming a data float period of 2 cycles (TDF_CYCLES = 2).
ation when controlled by NCS (READ_MODE = 0) and the TDF_CYCLES parameter equals 3.
• before starting a read access to a different external memory
• before starting a write access to the same device or to a different external one.
illustrates the Data Float Period in NRD-controlled mode (READ_MODE =1),
DF
will not slow down the execution of a program from internal
DF
) for each external memory device is programmed in the
Figure 21-22
AT91SAM9G20
shows the read oper-
179
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