Макросы:
.equ SCL1 = PA4 ;I2C port 1 SCL
.equ SDA1 = PA5 ;I2C port 1 SDA
.macro Port_SCL1_0 ;SCL1 = 0
sbi DDRA,SCL1
.endm
.macro Port_SCL1_Z ;SCL1 = Z
cbi DDRA,SCL1
.endm
.macro Port_SDA1_0 ;SDA1 = 0
sbi DDRA,SDA1
.endm
.macro Port_SDA1_Z ;SDA1 = Z
cbi DDRA,SDA1
.endm
.macro Skip_if_Port_SDA1_0 ;skip if SDA1 = 0 (pin)
sbic PINA,SDA1
.endm