INT E0 - DR Multiuser DOS - "A_READBLK" - READ STRING FROM AUX DEVICE
        CL = ACh
        DS:DX -> character control block (CHCB) (see below)
Return: AX = number of characters read
Desc:   read characters from the default auxiliary (AUXn:) device into a buffer
          until the buffer is full or the device is no longer ready
Notes:  if the device is initially not ready, blocks until at least one
          character has been read
        if another process owns AUX, this call blocks until the device becomes
          available
SeeAlso: INT E0/CL=03h,INT E0/CL=A5h,INT E0/CL=ADh

Format of character control block (CHCB):
Offset  Size    Description
 00h    DWORD   pointer to character buffer
 04h    WORD    length of character buffer

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