Symbols and Binary Code For Microinstruction Fields
• It is possible to create a symbolic language for microcode that is machine-translatable to binary code.
• Each line define a symbolic microinstruction with each column defining one of five fields:
– Label - Either blank or a name followed by a colon (indicates a potential branch)
– Microoperations - One, Two, Three Symbols, separated by commas (indicates that the microoperation being performed)
– CD - Either U, I, S or Z (indicates condition)
– BR - One of four two-bit numbers
– AD - A Symbolic Address, NEXT (address), RET, MAP (both of these last two converted to zeros by the assembler) (indicates the address of the next microinstruction)
• We will use the pseudoinstruction ORG to define the first instruction (or origin) of a microprogram, e.g., ORG 64 begins at 1000000.