Source register

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Source register (abbr. <sr>) is encoded in bits 5..3 of Register Operation (ROP) instructions.

The source registers are specified as follows:

MAC mnemonic Register name Value Octal value to add to ROP instruction
SD D register 1 108
SP Program counter 2 208
SB B register 3 308
SL L register 4 408
SA A register 5 508
ST T register 6 608
SX X register 7 708

If no source register is specified (value: 0), zero will be taken as the source register (i.e. the value 0 as input to operations).