101
ATmega103(L)
0945G–09/01
.
Table 37.
Pin Name Mapping
Signal Name in
Programming Mode
Pin Name
I/O
Function
RDY/BSY
PD1
O
0: Device is busy programming, 1: Device is ready
for new command
OE
PD2
I
Output Enable (active low)
WR
PD3
I
Write Pulse (active low)
BS1
PD4
I
Byte Select 1 (“0” selects low byte, “1” selects
high byte)
XA0
PD5
I
XTAL Action Bit 0
XA1
PD6
I
XTAL Action Bit 1
BS2
PD7
I
Byte Select 2 (always low)
PAGEL
PA0
I
Program Memory Page Load
DATA
PB7-0
I/O
Bi-directional Data Bus (output when OE is low)
Table 38.
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 39.
Command Byte Bit Coding
Command Byte
Command Executed
1000 0000
Chip Erase
0100 0000
Write Fuse Bits
0010 0000
Write Lock Bits
0001 0000
Write Flash
0001 0001
Write EEPROM
0000 1000
Read Signature Bytes
0000 0100
Read Lock and Fuse Bits
0000 0010
Read Flash
0000 0011
Read EEPROM