Int 21 Fn 40  - Turbo Debug Hardware Breakpoints - Send Cmd To Hardware B  [G]

   AH = 40h
   BX = handle for character device "TDHDEBUG"
   CX = number of bytes to write
   DS:DX -> hardware breakpoint command (see below)

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

Note:  results are retrieved by reading from the device

See Also: AH=3Fh"Turbo Debug"

Format of hardware breakpoint commands:
Offset Size    Description
 00h   BYTE    command code
       00h install interrupt vectors
       01h get hardware capabilities
       02h enable hardware breakpoints
       03h disable hardware breakpoints
       04h set hardware breakpoint
       05h clear hardware breakpoint
       06h set I/O base address and reset hardware
       07h restore interrupt vectors
---command code 00h---
 01h   DWORD   pointer to Turbo Debugger entry point to be jumped to on
       hardware breakpoint; call with CPU state the same as on
       the breakpoint except for pushing AX and placing an entry
       code (FFh if breakout button or breakpoint handle) in AH
---command code 04h---
 01h   BYTE    breakpoint type
       00h memory read
       01h memory write
       02h memory read/write
       03h I/O read
       04h I/O write
       05h I/O read/write
       06h instruction fetch
 02h   BYTE    address matching mode
       00h any address
       01h equal to test value
       02h different from test value
       03h above test value
       04h below test value
       05h below or equal to test value
       06h above or equal to test value
       07h within inclusive range
       08h outside specified range
 03h   DWORD   32-bit linear low address
 07h   DWORD   32-bit linear high address
 0Bh   WORD    pass count
 0Dh   BYTE    data size (01h, 02h, or 04h)
 0Eh   BYTE    source of matched bus cycle
       01h CPU
       02h DMA
       03h either
 0Fh   BYTE    data-matching mode
       00h match any
       01h equal to test value
       02h different from test value
       03h above test value
       04h below test value
       05h below or equal to test value
       06h above or equal to test value
       07h within specified range
       08h outside specified range
 10h   DWORD   low data value
 14h   DWORD   high data value
 18h   DWORD   data mask specifying which bits of the data are tested
---command code 05h---
 01h   BYTE    handle of breakpoint to clear (breakpoint returned from command
       04h)
---command code 06h---
 01h   WORD    base address of hardware debugger board