At89sx 8 bit microcontroller atmel at89s8253 24pu 8 bit microcontroller at89sx family 27v to 55v supply voltage 12kb flash memory 2kb eeprom memory 256bytes sram data memory 32 io pins 3 timers 24mhz clock speed uart spi interfaces 40 dip case the atmel at89s range are low voltage high performance cmos 8 bit microcontrollers that feature in system programmable isp flash program memory manufactured using atmels high density non volatile memory technology these devices are