Atmel STK502 - Manual (Page 16)

Using the STK502 Top Module
2-10 STK502 User Guide
2528A–AVR–11/02
2.6 TOSC Switch Figure 2-14. TOSC Switch
On the ATmega169 the TOSC1 and TOSC2 lines are shared with XTAL1 and XTAL2.
The TOSC switch selects whether the 32 kHz crystal on the STK502, or the XT1/XT2
signals from STK500 should be connected to these pins on the device.
Figure 2-15 shows a simplified block schematic on how this is implemented.
Figure 2-15. TOSC Block Schematic
XTAL1/TOSC1
AVR
XTAL2/TOSC2
XT1
XT2
TOSC
Switch
32 kHz
To
STK500