AT90USB647-MU Atmel, AT90USB647-MU Datasheet - Page 30

• Manufacturer Part Number: AT90USB647-MU
• Description: MCU, 8BIT, 64K FLASH, USB, 64QFN
• Manufacturer: Atmel

Specifications of AT90USB647-MU

• Controller Family/series: AT90
• No. Of I/o's: 48
• Eeprom Memory Size: 2KB
• Ram Memory Size: 4KB
• Cpu Speed: 16MHz
• No. Of: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 64KB
• Oscillator Type: External, Internal
• Package: 64QFN EP
• Device Core: AVR
• Family Name: AT90
• Maximum Speed: 20 MHz
• Ram Size: 4 KB
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 48
• Interface Type: SPI/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 4
• Lead Free Status / Rohs Status: Details

5.5
5.5.1
5.5.2
30
External Memory Interface
AT90USB64/128
Overview
Using the External Memory Interface
With all the features the External Memory Interface provides, it is well suited to operate as an
interface to memory devices such as External SRAM and Flash, and peripherals such as LCD-
display, A/D, and D/A. The main features are:
•
•
•
•
When the eXternal MEMory (XMEM) is enabled, address space outside the internal SRAM
becomes available using the dedicated External Memory pins (see
10-3 on page
Figure 5-4.
The interface consists of:
The control bits for the External Memory Interface are located in two registers, the External
Memory Control Register A – XMCRA, and the External Memory Control Register B – XMCRB.
• AD7:0: Multiplexed low-order address bus and data bus.
• A15:8: High-order address bus (configurable number of bits).
• ALE: Address latch enable.
• RD: Read strobe.
• WR: Write strobe.
Four different wait-state settings (including no wait-state).
Independent wait-state setting for different external Memory sectors (configurable sector size).
The number of bits dedicated to address high byte is selectable.
Bus keepers on data lines to minimize current consumption (optional).
79, and
External Memory with Sector Select
Table 10-9 on page
E xternal M emory
(0-60K x 8)
M emory C onfiguration A
83). The memory configuration is shown in
I nternal memory
L ower sector
U pper sector
SRW01
SRW00
SRW11
SRW10
0 x 0000
ISRAM end
XMem start
0 x FFFF
SRL[2..0]
Figure 2-1 on page
7593K–AVR–11/09
Figure
5,
Table
5-4.