3.7.3 Tcode Instruction Format

The following constants are used to extract specific parts of Tcode instructions:

TCODE.IOPMASK is a mask that is used to extract the opcode part of an instruction:

opcode := instruction & TCODE.IOPMASK;

The remaining bit masks and offsets operate on the Tcode flags field which is the most significant byte of a 16-bit word:

Flags := instruction >> 8;

The individual fields of a Tcode flags field are extracted as follows:

Argument_flag     := Flags & TCODE.IARFLAG >> TCODE.IAROFF;
Argument_count    := Flags & TCODE.IARMASK >> TCODE.IAMOFF;
Argument_1_len    := Flags & TCODE.IL1MASK >> TCODE.IL1OFF;
Argument_2_len    := Flags & TCODE.IL2MASK >> TCODE.IL2OFF;
Argument_str_flag := Flags & TCODE.ISTFLAG >> TCODE.ISFOFF;