Record types in abmtypes.vhd
ipacket - defines an instruction (opcode, pflag, dest, src1, src2, immv). Passed from fetch to drr.
CRSpacket - defines an issued instruction (opcode, pflag, dest, src1, src1_valid, src2, src2_valid, immv, valid). Passed from drr to crs.
- valid flag only used within CRS to mark shelf entry as free or empty.
Epacket - defines a dispatched instruction (opcode, pflag, dest, src1, src2, immv). Passed from crs to execution units.