Int 21 Fn 3F  - Turbo Debug Hardware Breakpoints - Read Status Block       [G]

   AH = 3Fh
   BX = handle for character device "TDHDEBUG"
   CX = number of bytes to read
   DS:DX -> buffer for status block (see below)

Return: CF clear if successful
       AX = number of bytes actually read
   CF set on error
       AX = error code (05h,06h) (see AH=59h)

See Also: AH=40h"Turbo Debug"

Values for status of command:
 00h   successful
 01h   invalid handle
 02h   no more breakpoints available
 03h   hardware does not support specified breakpoint type
 04h   previous command prevents execution
 05h   debugger hardware not found
 06h   hardware failure
 07h   invalid command
 08h   driver not initialized yet
 FEh   recursive entry (hardware breakpoint inside hw bp handler)

Format of status block:
Offset Size    Description
 00h   BYTE    status of command (see above)
---status for command 01h---
 01h   WORD    device driver interface version number (currently 1)
 03h   WORD    device driver software version
 05h   BYTE    maximum simultaneous hardware breakpoints
 06h   BYTE    configuration bits (see below)
 07h   BYTE    supported breakpoint types (see below)
 08h   WORD    supported addressing match modes (see below)
 0Ah   WORD    supported data matches (see below)
 0Ch   BYTE    maximum data match length (01h, 02h, or 04h)
 0Dh   WORD    size of onboard memory (in KB)
 0Fh   WORD    maximum number of trace-back events
 11h   WORD    hardware breakpoint enable byte address segment (0000h if not
       supported)
---status for command 04h---
 01h   BYTE    handle to use when referring to the just-set breakpoint

Bitfields for configuration bits:
 bit 0 CPU and DMA accesses are distinct
 bit 1 can detect DMA transfers
 bit 2 supports data mask
 bit 3 hardware pass counter on breakpoints
 bit 4 can match on data as well as addresses

Bitfields for supported breakpoint types:
 bit 0 memory read
 bit 1 memory write
 bit 2 memory read/write
 bit 3 I/O read
 bit 4 I/O write
 bit 5 I/O read/write
 bit 6 instruction fetch

Bitfields for supported addressing match modes:
 bit 0 any address
 bit 1 equal to test value
 bit 2 not equal
 bit 3 above test value
 bit 4 below test value
 bit 5 below or equal
 bit 6 above or equal
 bit 7 within range
 bit 8 outside range

Bitfields for supported data matches:
 bit 0 any data
 bit 1 equal to test value
 bit 2 not equal
 bit 3 above test value
 bit 4 below test value
 bit 5 below or equal
 bit 6 above or equal
 bit 7 within range
 bit 8 outside range