301
2467S–AVR–07/09
ATmega128
Figure 144.
SPI Serial Programming and Verify
Notes:
1. If the device is clocked by the Internal Oscillator, it is no need to connect a clock source to the
XTAL1 pin.
2. V
CC
- 0.3V < AVCC < V
CC
+ 0.3V, however, AVCC should always be within 2.7 - 5.5V.
When programming the EEPROM, an auto-erase cycle is built into the self-timed programming
operation (in the serial mode ONLY) and there is no need to first execute the Chip Erase instruc-
tion. The Chip Erase operation turns the content of every memory location in both the Program
and EEPROM arrays into $FF.
Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high periods
for the serial clock (SCK) input are defined as follows:
Low:> 2 CPU clock cycles for f
ck
< 12 MHz, 3 CPU clock cycles for f
ck
12 MHz
High:> 2 CPU clock cycles for f
ck
< 12 MHz, 3 CPU clock cycles for f
ck
12 MHz
SPI Serial
Programming
Algorithm
When writing serial data to the ATmega128, data is clocked on the rising edge of SCK.
When reading data from the ATmega128, data is clocked on the falling edge of SCK. See
for timing details.
To program and verify the ATmega128 in the SPI Serial Programming mode, the following
sequence is recommended (See four byte instruction formats in
):
1.
Power-up sequence:
Apply power between V
CC
and GND while RESET and SCK are set to “0”. In some sys-
tems, the programmer can not guarantee that SCK is held low during power-up. In this
case, RESET must be given a positive pulse of at least two CPU clock cycles duration
after SCK has been set to “0”.
As an alternative to using the RESET signal, PEN can be held low during Power-on
Reset while SCK is set to “0”. In this case, only the PEN value at Power-on Reset is
important. If the programmer cannot guarantee that SCK is held low during power-up, the
PEN method cannot be used. The device must be powered down in order to commence
normal operation when using this method.
2.
Wait for at least 20 ms and enable SPI Serial Programming by sending the Programming
Enable serial instruction to pin MOSI.
VCC
GND
XTAL1
SCK
PDO
PDI
RESET
PE0
PE1
PB1
+2.7 - 5.5V
AVCC
+2.7 - 5.5V
(2)
