ATmega8U2/16U2/32U2
Table 25-9. Pin Name Mapping
Signal Name in
Programming Mode
Pin Name
PD7
I/O
Function
PAGEL
BS2
I
I
Program Memory and EEPROM data Page Load.
Byte Select 2.
PC6
DATA
PB7-0
I/O
Bi-directional Data bus (Output when OE is low).
Table 25-10. BS2 and BS1 Encoding
Flash Data
Loading /
Reading
Flash / EEPROM
Fuse
Programming
Reading Fuse
and Lock Bits
BS2
0
BS1
0
Address
Low Byte
High Byte
Low Byte
High Byte
Low Byte
High Byte
Fuse Low Byte
Lockbits
0
1
Extended High
Byte
Extended Fuse
Byte
1
1
0
1
Reserved
Reserved
Extended Byte
Reserved
Reserved
Fuse High Byte
Table 25-11. Pin Values Used to Enter Programming Mode
Pin
PAGEL
XA1
Symbol
Value
Prog_enable[3]
Prog_enable[2]
Prog_enable[1]
Prog_enable[0]
0
0
0
0
XA0
BS1
Table 25-12. XA1 and XA0 Encoding
XA1
XA0
Action when XTAL1 is Pulsed
Load Flash or EEPROM Address (High or low address byte determined
by BS2 and BS1).
0
0
0
1
1
1
0
1
Load Data (High or Low data byte for Flash determined by BS1).
Load Command
No Action, Idle
Table 25-13. Command Byte Bit Encoding
Command Byte
1000 0000
Command Executed
Chip Erase
0100 0000
Write Fuse bits
Write Lock bits
Write Flash
0010 0000
0001 0000
251
7799D–AVR–11/10
ATMEL [ ATMEL ]
