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From CoCopedia - The Tandy/Radio Shack Color Computer Wiki
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The SAM or Synchronous Address Multiplexer is a chip that controls access to RAM memory by the 6809 CPU and the VDG (Video Display Generator).

SAM Registers

Address Shorthand name Function Effect
FFC0 V0CLR SAM V0 bit clear
FFC1 V0SET SAM V0 bit set
FFC2 V1CLR SAM V1 bit clear
FFC3 V1SET SAM V1 bit set
FFC4 V2CLR SAM V2 bit clear
FFC5 V2SET SAM V2 bit set
FFC6 F0CLR SAM F0 bit clear
FFC7 F0SET SAM F0 set bit add $200 to video offset
FFC8 F1CLR SAM F1 clear bit
FFC9 F1SET SAM F1 set bit add $400 to video offset
FFCA F2CLR SAM F2 bit clear
FFCB F2SET SAM F2 set bit add $800 to video offset
FFCC F3CLR SAM F3 bit clear
FFCD F3SET SAM F3 set bit add $1000 to video offset
FFCE F4CLR SAM F4 bit clear
FFCF F4SET SAM F4 set bit $2000 to video offset
FFD0 F5CLR SAM F5 bit clear
FFD1 F5SET SAM F5 set bit add $4000 to video offset
FFD2 F6CLR SAM F6 bit clear
FFD3 F6SET SAM F6 set bit add $8000 to video offset