Datasheet
193
ATmega323(L)
1457E–11/01
Programming Times for
Nonvolatile Memory
The internal RC oscillator is used to control programming time when programming or
erasing Flash, EEPORM, fuses, and lock bits. During parallel or serial programming, the
device is in reset, and this oscillator runs at its initial, uncalibrated frequency, which may
vary from 0.5 MHz to 1.0 MHz. In software it is possible to calibrate this oscillator to 1.0
MHz (see “Calibrated Internal RC Oscillator” on page 40). Consequently, programming
times will be shorter and more accurate when programming or erasing nonvolatile mem-
ory from software, using SPM or the EEPROM interface. See Table 68 for a summary of
programming times.
Notes: 1. Includes variation over voltage and temperature after RC oscillator has been cali-
brated to 1.0 MHz
2. Parallel EEPROM programming takes 1K cycles
Figure 99. Serial Programming Waveforms
Table 68. Maximum Programming Times for Nonvolatile Memory
Operation Symbol
Number of
RC Oscillator
Cycles
Parallel/serial programming Self-
programming
(1)
2.7V 5.0V
Chip Erase t
WD_CE
16K 32 ms 30 ms 17 ms
Flash Write t
WD_FLASH
8K 16 ms 15 ms 8.5 ms
EEPROM
Write
(2)
t
WD_EEPROM
2K 4 ms 3.8 ms 2.2 ms
Fuse/lock
bit write
t
WD_FUSE
1K 2 ms 1.9 ms 1.1 ms
MSB
MSB
LSB
LSB
SERIAL CLOCK INPUT
PB7(SCK)
SERIAL DATA INPUT
PB5 (MOSI)
PB6 (MISO)
SAMPLE
SERIAL DATA OUTPUT