Datasheet

Table Of Contents
339
ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]
2549Q–AVR–02/2014
30.8.1 Serial Programming Pin Mapping
Figure 30-10. Serial Programming and Verify
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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 1.8V - 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 instruction. The Chip Erase operation turns the content of every
memory location in both the Program and EEPROM arrays into 0xFF.
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
< 12MHz, 3 CPU clock cycles for f
ck
>= 12MHz
High: > 2 CPU clock cycles for f
ck
< 12MHz, 3 CPU clock cycles for f
ck
>= 12MHz
30.8.2 Serial Programming Algorithm
When writing serial data to the ATmega640/1280/1281/2560/2561, data is clocked on the rising edge of SCK.
When reading data from the ATmega640/1280/1281/2560/2561, data is clocked on the falling edge of SCK. See
Figure 30-12 on page 342 for timing details.
To program and verify the ATmega640/1280/1281/2560/2561 in the serial programming mode, the following
sequence is recommended (see four byte instruction formats in Table 30-17 on page 340):
1. Power-up sequence:
Apply power between V
CC
and GND while RESET and SCK are set to “0”. In some systems, the program-
mer 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”.
2. Wait for at least 20ms and enable serial programming by sending the Programming Enable serial instruction
to pin PDI.
Table 30-15. Pin Mapping Serial Programming
Symbol Pins (TQFP-100) Pins (TQFP-64) I/O Description
PDI PB2 PE0 I Serial Data in
PDO PB3 PE1 O Serial Data out
SCK PB1 PB1 I Serial Clock
VCC
GND
XT AL1
SCK
PDO
PDI
RESET
+1.8V - 5.5V
AVCC
+1.8V - 5.5V
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