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9.5 IDT Descriptors

The IDT may contain any of three kinds of descriptor:

   -  Task gates
   -  Interrupt gates
   -  Trap gates
Figure 9-3 illustrates the format of task gates and 80386 interrupt gates and trap gates. (The task gate in an IDT is the same as the task gate already discussed in Chapter 7.)

Figure 9-3. 80306 IDT Gate Descriptors

                                80386 TASK GATE
   31                23                15                7                0
  +-----------------+-----------------+---+---+---------+-----------------+
  |#############(NOT USED)############| P |DPL|0 0 1 0 1|###(NOT USED)####|4
  |-----------------------------------+---+---+---------+-----------------|
  |             SELECTOR              |#############(NOT USED)############|0
  +-----------------+-----------------+-----------------+-----------------+

                                80386 INTERRUPT GATE
   31                23                15                7                0
  +-----------------+-----------------+---+---+---------+-----+-----------+
  |           OFFSET 31..16           | P |DPL|0 1 1 1 0|0 0 0|(NOT USED) |4
  |-----------------------------------+---+---+---------+-----+-----------|
  |             SELECTOR              |           OFFSET 15..0            |0
  +-----------------+-----------------+-----------------+-----------------+

                                80386 TRAP GATE
   31                23                15                7                0
  +-----------------+-----------------+---+---+---------+-----+-----------+
  |          OFFSET 31..16            | P |DPL|0 1 1 1 1|0 0 0|(NOT USED) |4
  |-----------------------------------+---+---+---------+-----+-----------|
  |             SELECTOR              |           OFFSET 15..0            |0
  +-----------------+-----------------+-----------------+-----------------+


Prev: 9.4 Interrupt Descriptor Table
Next: 9.6 Interrupt Tasks and Interrupt Procedures