Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 300
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Table 27-9. 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.
XA0 PD5 I XTAL Action Bit 0
XA1 PD6 I XTAL Action Bit 1
PAGEL PD7 I Program Memory and EEPROM data Page Load.
BS2 PA0 I Byte Select 2.
DATA PB7-0 I/O Bi-directional Data bus (Output when OE is low).
Table 27-10. BS2 and BS1 encoding
BS2 BS1
Flash / EEPROM
address
Flash data loading /
reading Fuse programming Reading fuse and lock bits
0 0 Low Byte Low Byte Low Byte Fuse Low Byte
0 1 High Byte High Byte High Byte Lockbits
1 0
Extended High
Byte
Reserved Extended Byte Extended Fuse Byte
1 1 Reserved Reserved Reserved Fuse High Byte
Table 27-11. Pin values used to enter Programming mode
Pin Symbol Value
PAGEL Prog_enable[3] 0
XA1 Prog_enable[2] 0
XA0 Prog_enable[1] 0
BS1 Prog_enable[0] 0
Table 27-12. XA1 and XA0 enoding
XA1 XA0 Action when XTAL1 is pulsed
0 0 Load Flash or EEPROM Address (High or low address byte determined by BS2 and BS1)
0 1 Load Data (High or Low data byte for Flash determined by BS1)
1 0 Load Command
1 1 No Action, Idle