I think (after quick look at kzhd.djvu) that dec's controller was derived from wd1000 (at least the fast select layout looks similar) and I've tried disassembling its firmware, but something is wrong (python 3.4.3):

% /tmp/s8x30x/dis8x30x /tmp/kr1656re3-4.bin /tmp/kr1656re3-5.bin 
Traceback (most recent call last):
  File "/tmp/s8x30x/dis8x30x", line 116, in <module>
    disassemble(s8x30x, memory, show_obj = args.listing, output_file = args.output)
  File "/tmp/s8x30x/dis8x30x", line 59, in disassemble
    symtab_by_value = pass1(s8x30x, fw, base)
  File "/tmp/s8x30x/dis8x30x", line 30, in pass1
    (dis, operands, fields) = s8x30x.disassemble_inst(fw, pc, disassemble_operands = False)
  File "/tmp/s8x30x/s8x30x.py", line 354, in disassemble_inst
    inst, form, fields = self.inst_search(fw, pc)
  File "/tmp/s8x30x/s8x30x.py", line 339, in inst_search
    form, fields = self.form_search(fw, pc, inst)
  File "/tmp/s8x30x/s8x30x.py", line 315, in form_search
    if OT.sr in form.operands and not sr.is_src_reg():
  File "/tmp/s8x30x/s8x30x.py", line 84, in is_src_reg
    if self >= self.liv0:
AttributeError: 'Reg' object has no attribute 'liv0'