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PCF1_ADD EQU 01000101b ; I2C expander 1 
PCF2_ADD EQU 01001101b ; I2C expander 2 

RES_1 EQU 0x00 ; 100k ohms 
RES_2 EQU 0x01 ; 10k ohms  these are integer values for 2-bit select lines 
RES_3 EQU 0x02 ; 1k ohm 
RES_4 EQU 0x03 ; 0.1k ohms 

BYE_BITS DATA 0x40 ; 8-bit register for counting down 8 units 
MUX_NO DATA 0x41 ; 8-bit register for holding an ID number 

NACK BIT 0x50 ; Acknowledge flag for I2C 
PCF_2 BIT 0x51 ; I2C expander select flag 

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