STK504 Datasheet, PDF (12/21 Pages) ATMEL Corporation – Supports the ATmega3290 and ATmega6490 with built-in LCD controller

STK504 Clock Sources
The STK504 can supply three kinds of external clock sources to the AVR
mounted in the ZIF socket: On-board 32kHz crystal, a higher frequency crystal
mounted in the on-board socket and a clock supplied from STK500.
The clock switch
The clock switch has three positions, EXT, LF and HF as shown in figure 5-1.
See table 5-1 for function.
Table 5-1: Clock switch positions
Position
EXT
LF
HF
Function
Clock from STK500. (See STK500
documentation for more information.)
On-board 32kHz crystal
Crystal placed in the socket marked HF
on STK504
Figure 5-1: Clock switch
EXT – STK500 as clock source
If you put the switch in the EXT position, you will supply the externally generated
clock (from STK500) to the XTAL/TOSC pins of the AVR. Check the STK500
help file for more information on how to set the different clock options.
LF – Low-Frequency 32kHz crystal
The STK504 has a 32kHz (32,768Hz) crystal that can be connected to the
XTAL/TOSC pins when the switch is set to the LF position.
HF – High-Frequency crystal
12