Pin Values Used To Enter Programming Mode; Xa1 And Xa0 Coding; Command Byte Bit Coding - Atmel ATmega128 Manual

2467S–AVR–07/09
Table 120. Pin Name Mapping (Continued)
Signal Name in
Programming Mode Pin Name
XA1
PAGEL
BS2
DATA
Table 121. Pin Values Used to Enter Programming Mode
Pin
PAGEL
XA1
XA0
BS1
Table 122. XA1 and XA0 Coding
XA1 XA0 Action when XTAL1 is Pulsed
0 0 Load Flash or EEPROM Address (High or low address byte determined by BS1)
0 1 Load Data (High or Low data byte for Flash determined by BS1)
1 0 Load Command
1 1 No Action, Idle
Table 123. Command Byte Bit Coding
Command Byte
1000 0000
0100 0000
0010 0000
0001 0000
0001 0001
0000 1000
0000 0100
0000 0010
0000 0011
I/O Function
PD6 I XTAL Action Bit 1
PD7 I Program Memory and EEPROM data Page Load
Byte Select 2 ("0" selects low byte, "1" selects 2'nd
PA0 I
high byte)
PB7-0 I/O Bi-directional Data bus (Output when OE is low)
Symbol
Prog_enable[3]
Prog_enable[2]
Prog_enable[1]
Prog_enable[0]
Command Executed
Chip Erase
Write Fuse bits
Write Lock bits
Write Flash
Write EEPROM
Read Signature Bytes and Calibration byte
Read Fuse and Lock bits
Read Flash
Read EEPROM
ATmega128
Value
0
0
0
0
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