atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 267

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

27.2.1
27.3
27.4
27.5
27.5.1
2570L–AVR–08/07
Signature Bytes
Calibration Byte
Parallel Programming Parameters, Pin Mapping, and Commands
Latching of Fuses
Signal Names
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if
Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.
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 three-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 ATmega325/3250/645/6450 the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x001: 0x95/0x96 (indicates Flash memory,refer to
3. 0x002: 0x05/0x06 (indicates device, refer to
The ATmega325/3250/645/6450 has a byte calibration value for the internal RC Oscillator. This
byte resides in the high byte of address 0x000 in the signature address space. During reset, this
byte is automatically written into the OSCCAL Register to ensure correct frequency of the cali-
brated RC Oscillator.
This section describes how to parallel program and verify Flash Program memory, EEPROM
Data memory, Memory Lock bits, and Fuse bits in the ATmega325/3250/645/6450. Pulses are
assumed to be at least 250ns unless otherwise noted.
In this section, some pins of the ATmega325/3250/645/6450 are referenced by signal names
describing their functionality during parallel programming, see
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 positive pulse.
The bit coding is shown in
When pulsing WR or OE, the command loaded determines the action executed. The different
Commands are shown in
Table
Table
27-9.
27-8.
ATmega325/3250/645/6450
“Part Number” on page
“Part Number” on page
Figure 27-1
224).
and
Table
224).
27-6. Pins
267