A Macro-Assembler Technique for Generating Control Words for a Micro-Programmed Processor

To produce microcode for an experimental system, such as FASTBUS interfaces, with wide control words and many micro-fields, one needs a micro-assembler which 1) allows wide flexibility in defining defaults for microcode fields, 2) does a significant amount of error checking to prevent multiple or inconsistant definitions of fields, 3) allows macro expansions which define several microcode words for frequently used sequences, and 4) is easily modified as hardware definitions are refined. Using MACRO-il on DEC PDP-11 computers, a library of macros has been created, which can be used to generate the 80-bit microcode words needed for a Unibus to FASTBUS micro-programmed interface and which meets the above requirements. The same technique could easily be used to develop libraries appropriate for other microcoded devices.