Datasheet

Table Of Contents
28
ATmega32A [DATASHEET]
Atmel-8155D-AVR-ATmega32A-Datasheet_02/2014
Note: 1. The device is shipped with this option selected.
When this Oscillator is selected, start-up times are determined by the SUT fuses as shown in Table 9-9. XTAL1
and XTAL2 should be left unconnected (NC).
Note: 1. The device is shipped with this option selected.
9.8 External Clock
To drive the device from an external clock source, XTAL1 should be driven as shown in Figure 9-4 on page 28. To
run the device on an external clock, the CKSEL fuses must be programmed to “0000”. By programming the
CKOPT Fuse, the user can enable an internal 36pF capacitor between XTAL1 and GND.
Figure 9-4. External Clock Drive Configuration
Table 9-8. Internal Calibrated RC Oscillator Operating Modes
CKSEL3:0 Nominal Frequency (MHz)
0001
(1)
1.0
0010 2.0
0011 4.0
0100 8.0
Table 9-9. Start-up Times for the Internal Calibrated RC Oscillator Clock Selection
SUT1:0
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
(V
CC
= 5.0V) Recommended Usage
00 6 CK BOD enabled
01 6 CK 4.1ms Fast rising power
10
(1)
6 CK 65ms Slowly rising power
11 Reserved
EXTERNAL
CLOCK
SIGNAL