ATMEGA64-16AI Atmel, ATMEGA64-16AI Datasheet - Page 34

• Manufacturer Part Number: ATMEGA64-16AI
• Description: IC AVR MCU 64K 16MHZ IND 64-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA64-16AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

XMCRB – External
Memory Control
Register B
2490Q–AVR–06/10
• Bit 7 – XMBK: External Memory Bus Keeper Enable
Writing XMBK to one enables the Bus Keeper on the AD7:0 lines. When the Bus Keeper is
enabled, it will ensure a defined logic level (zero or one) on AD7:0 when they would otherwise
be tri-stated. Writing XMBK to zero disables the Bus Keeper. XMBK is not qualified with SRE, so
even if the XMEM interface is disabled, the Bus Keepers are still activated as long as XMBK is
one.
• Bit 6..3 – Res: Reserved Bits
These are reserved bits and will always read as zero. When writing to this address location,
write these bits to zero for compatibility with future devices.
• Bit 2..0 – XMM2, XMM1, XMM0: External Memory High Mask
When the External Memory is enabled, all Port C pins are default used for the high address byte.
If the full 60 Kbytes address space is not required to access the external memory, some, or all,
Port C pins can be released for normal port pin function as described in
“Using all 64Kbytes Locations of External Memory” on page
bits to access all 64 Kbytes locations of the external memory.
Table 5. Port C Pins Released as Normal Port Pins when the External Memory is Enabled
Bit
(0x6C)
Read/Write
Initial Value
XMM2
0
0
0
0
1
1
1
1
XMM1
0
0
1
1
0
0
1
1
XMBK
R/W
7
0
XMM0
0
1
0
1
0
1
0
1
R
6
–
0
# Bits for External Memory Address
8 (Full 60 Kbytes space)
7
6
5
4
3
2
No Address high bits
R
5
–
0
R
4
–
0
R
3
–
0
XMM2
R/W
2
0
36, it is possible to use the XMMn
XMM1
R/W
1
0
Released Port Pins
None
PC7
PC7 - PC6
PC7 - PC5
PC7 - PC4
PC7 - PC3
PC7 - PC2
Full Port C
ATmega64(L)
Table
XMM0
R/W
0
0
5. As described in
XMCRB
34