Specifications

8
AVR064
2529A–AVR–11/02
ATmega169 Firmware The firmware that realizes the temperature control application is written in IAR EWAVR
2.27b. The timing related functions are written for an ATmega169 running at 1 Mhz
except the RTC clock and the LCD frame rate which is clocked from an external 32 kHz
crystal. The crystal is mounted on the STK502 board.
Interrupts Used
LCD Start of Frame In this interrupt the data from the LCD_displayData buffer is latched to the LCD Data
Registers. The variable LCD_Blink toggles every time this interrupt occurs. The interrupt
is dependent of the external 32 kHz crystal.
Timer/Counter2 Overflow This interrupt is used to increment the variable SECOND, which the whole RTC clock
builds on. Timer/Counter2 is clocked asynchronous from the 32 kHz and is therefore
independent of the clock frequency.
USART0, RX Complete This interrupt takes care of incoming data from the UART interface.
USART0, Data Register Empty This interrupt transmits data out through the UART interface.