AT91SAM9G45-EKES Atmel, AT91SAM9G45-EKES Datasheet - Page 205
AT91SAM9G45-EKES
Manufacturer Part Number
AT91SAM9G45-EKES
Description
KIT EVAL FOR AT91SAM9G45
Manufacturer
Atmel
Series
AT91SAM Smart ARMr
Type
MCUr
Datasheets
1.AT91SAM9G45-EKES.pdf
(56 pages)
2.AT91SAM9G45-EKES.pdf
(1218 pages)
3.AT91SAM9G45-EKES.pdf
(66 pages)
Specifications of AT91SAM9G45-EKES
Contents
Board
Processor To Be Evaluated
SAM9G45
Data Bus Width
32 bit
Interface Type
I2C, SPI, UART
Maximum Operating Temperature
+ 50 C
Minimum Operating Temperature
- 10 C
Operating Supply Voltage
1.8 V to 3.3 V
For Use With/related Products
AT91SAM9G45
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
Q4626953
- Current page: 205 of 1218
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21.10 Data Float Wait States
21.10.1
6438F–ATARM–21-Jun-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 21-20
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 21-21
AT91SAM9G45
shows the read oper-
205
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