ATmega1280 Atmel Corporation, ATmega1280 Datasheet - Page 30

• Manufacturer Part Number: ATmega1280
• Manufacturer: Atmel Corporation

Specifications of ATmega1280

• Flash (kbytes): 128 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 86
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 5
• Twi (i2c): 1
• Uart: 4
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 8
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 6
• Output Compare Channels: 16
• Input Capture Channels: 4
• Pwm Channels: 15
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

9.1.3
9.1.4
2549N–AVR–05/11
Pull-up and Bus-keeper
Timing
Figure 9-2.
The pull-ups on the AD7:0 ports may be activated if the corresponding Port register is written to
one. To reduce power consumption in sleep mode, it is recommended to disable the pull-ups by
writing the Port register to zero before entering sleep.
The XMEM interface also provides a bus-keeper on the AD7:0 lines. The bus-keeper can be dis-
abled and enabled in software as described in
on page
these lines are tri-stated by the XMEM interface.
External Memory devices have different timing requirements. To meet these requirements, the
XMEM interface provides four different wait-states as shown in
tant to consider the timing specification of the External Memory device before selecting the wait-
state. The most important parameters are the access time for the external memory compared to
the set-up requirement. The access time for the External Memory is defined to be the time from
receiving the chip select/address until the data of this address actually is driven on the bus. The
access time cannot exceed the time from the ALE pulse must be asserted low until data is stable
during a read sequence (see t
379
to divide the external memory space in two sectors with individual wait-state settings. This
makes it possible to connect two different memory devices with different timing requirements to
the same XMEM interface. For XMEM interface timing details, please refer to
page 379
in the
Note that the XMEM interface is asynchronous and that the waveforms in the following figures
are related to the internal system clock. The skew between the internal and external clock
(XTAL1) is not guarantied (varies between devices temperature, and supply voltage). Conse-
quently, the XMEM interface is not suited for synchronous operation.
- 382). The different wait-states are set up in software. As an additional feature, it is possible
“External Data Memory Timing” on page
38. When enabled, the bus-keeper will keep the previous value on the AD7:0 bus while
to
Table 31-18 on page 382
External SRAM Connected to the AVR
AVR
AD7:0
A15:8
ALE
WR
RD
LLRL
ATmega640/1280/1281/2560/2561
+ t
RLRH
and
- t
Figure 31-9 on page 382
DVRH
D
G
“XMCRB – External Memory Control Register B”
379.
in
Tables 31-11
Q
Table 9-3 on page
through
D[7:0]
A[15:8]
A[7:0]
RD
WR
SRAM
to
Figure 31-12 on page 384
Tables 31-18
Table 31-11 on
38. It is impor-
on pages
30