ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 293

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Latching of Fuses
Signature Bytes
Calibration Byte
Parallel Programming
Parameters, Pin
Mapping, and
Commands
Signal Names
2490G–AVR–03/04
The fuse values are latched when the device enters Programming mode and changes of
the fuse values will have no effect until the part leaves Programming mode. This does
not apply to the EESAVE Fuse which will take effect once it is programmed. The fuses
are also latched on Power-up in Normal mode.
All Atmel microcontrollers have a 3-byte signature code which identifies the device. This
code can be read in both Serial and Parallel mode, also when the device is locked. The
three bytes reside in a separate address space.
For the ATmega64 the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel)
2. 0x001: 0x96 (indicates 64KB Flash memory)
3. 0x002: 0x02 (indicates ATmega64 device when 0x001 is 0x96)
The ATmega64 stores four different calibration values for the internal RC Oscillator.
These bytes resides in the signature row high byte of the addresses 0x000, 0x0001,
0x0002, and 0x0003 for 1, 2, 4, and 8 MHz respectively. During Reset, the 1 MHz value
is automatically loaded into the OSCCAL Register. If other frequencies are used, the
calibration value has to be loaded manually, see “Oscillator Calibration Register – OSC-
CAL(1)” on page 40 for details.
This section describes how to parallel program and verify Flash Program memory,
EEPROM Data memory, Memory Lock bits, and Fuse bits in the ATmega64. Pulses are
assumed to be at least 250 ns unless otherwise noted.
In this section, some pins of the ATmega64 are referenced by signal names describing
their functionality during parallel programming, see Figure 138 and Table 121. Pins not
described in the following table are referenced by pin names.
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a posi-
tive pulse. The bit coding is shown in Table 123.
When pulsing WR or OE, the command loaded determines the action executed. The dif-
ferent Commands are shown in Table 124.
ATmega64(L)
293