ATmega8(L)
Erratas
The revision letter in this section refers to the revision of the ATmega8 device.
ATmega8
Rev. D, E, F, and G
• CKOPT Does not Enable Internal Capacitors on XTALn/TOSCn Pins when 32 KHz
Oscillator is Used to Clock the Asynchronous Timer/Counter2
1. CKOPT Does not Enable Internal Capacitors on XTALn/TOSCn Pins when
32 KHz Oscillator is Used to Clock the Asynchronous Timer/Counter2
When the internal RC Oscillator is used as the main clock source, it is possible to
run the Timer/Counter2 asynchronously by connecting a 32 KHz Oscillator between
XTAL1/TOSC1 and XTAL2/TOSC2. But when the internal RC Oscillator is selected
as the main clock source, the CKOPT Fuse does not control the internal capacitors
on XTAL1/TOSC1 and XTAL2/TOSC2. As long as there are no capacitors con-
nected to XTAL1/TOSC1 and XTAL2/TOSC2, safe operation of the Oscillator is not
guaranteed.
Problem fix/Workaround
Use external capacitors in the range of 20 - 36 pF on XTAL1/TOSC1 and
XTAL2/TOSC2. This will be fixed in ATmega8 Rev. G where the CKOPT Fuse will
control internal capacitors also when internal RC Oscillator is selected as main clock
source. For ATmega8 Rev. G, CKOPT = 0 (programmed) will enable the internal
capacitors on XTAL1 and XTAL2. Customers who want compatibility between Rev.
G and older revisions, must ensure that CKOPT is unprogrammed (CKOPT = 1).
291
2486M–AVR–12/03
ATMEL [ ATMEL ]
