AT91SAM7SE256B-AU Atmel, AT91SAM7SE256B-AU Datasheet - Page 207
AT91SAM7SE256B-AU
Manufacturer Part Number
AT91SAM7SE256B-AU
Description
IC ARM7 MCU FLASH 256K 128-LQFP
Manufacturer
Atmel
Series
AT91SAMr
Datasheet
1.AT91SAM7SE256-AU.pdf
(673 pages)
Specifications of AT91SAM7SE256B-AU
Core Processor
ARM7
Core Size
16/32-Bit
Speed
55MHz
Connectivity
EBI/EMI, I²C, SPI, SSC, UART/USART, USB
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
88
Program Memory Size
256KB (256K x 8)
Program Memory Type
FLASH
Ram Size
32K x 8
Voltage - Supply (vcc/vdd)
1.65 V ~ 1.95 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
*
Core
ARM7TDMI
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Lead Free Status / Rohs Status
Details
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
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23.6.4
Figure 23-6. Refresh Cycle Followed by a Read Access
6222F–ATARM–14-Jan-11
D[31:0]
A[12:0]
SDWE
SDCS
SDCK
(input)
RAS
CAS
Row n
col c col d
SDRAM Controller Refresh Cycles
Dnb
Dnc
Dnd
An auto-refresh command is used to refresh the SDRAM device. Refresh addresses are gener-
ated internally by the SDRAM device and incremented after each auto-refresh automatically.
The SDRAM Controller generates these auto-refresh commands periodically. A timer is loaded
with the value in the register SDRAMC_TR that indicates the number of clock cycles between
refresh cycles.
A refresh error interrupt is generated when the previous auto-refresh command did not perform.
It will be acknowledged by reading the Interrupt Status Register (SDRAMC_ISR).
When the SDRAM Controller initiates a refresh of the SDRAM device, internal memory
accesses are not delayed. However, if the CPU tries to access the SDRAM, the slave will indi-
cate that the device is busy and the ARM BWAIT signal will be asserted. See
t
RP
= 3
t
RC
SAM7SE512/256/32 Preliminary
= 8
Row m
t
RCD
= 3
col a
Figure 23-6
CAS = 2
Dma
below.
207
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