AT91SAM9261-CJ-999 Atmel, AT91SAM9261-CJ-999 Datasheet - Page 179
AT91SAM9261-CJ-999
Manufacturer Part Number
AT91SAM9261-CJ-999
Description
IC MCU ARM9 ULTRA LP 217LFBGA
Manufacturer
Atmel
Series
AT91SAMr
Datasheet
1.AT91SAM9261-CJ-999.pdf
(749 pages)
Specifications of AT91SAM9261-CJ-999
Core Processor
ARM9
Core Size
16/32-Bit
Speed
190MHz
Connectivity
EBI/EMI, I²C, MMC, SPI, SSC, UART/USART, USB
Peripherals
DMA, LCD, POR, PWM, WDT
Number Of I /o
96
Program Memory Size
32KB (32K x 8)
Program Memory Type
ROM
Ram Size
192K x 8
Voltage - Supply (vcc/vdd)
1.08 V ~ 1.32 V
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
217-LFBGA
For Use With
AT91SAM9261-EK - KIT EVAL FOR AT91SAM926EJ-SAT91SAM-ICE - EMULATOR FOR AT91 ARM7/ARM9
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Data Converters
-
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21.10 Data Float Wait States
21.10.1
6062M–ATARM–23-Mar-09
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
AT91SAM9261 Preliminary
Figure 21-21
shows the read oper-
179
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