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1.1 root 1: TITLE CURSOR
2:
3: ; This file exports the function _GetCurLoc which gets the location
4: ; of the cursor on the CRT screen.
5: ;
6: ; This routine illustrates the use of the DosPortAccess() call. This
7: ; call is supposed to give the IOPL segment access to ports and CLI/STI
8: ; instructions. In fact, on the PC/AT (80286) there is no enforcement.
9: ; This call is provided for future compatibility with the 80386.
10: ; At present, the use of DosPortAccess() from an IOPL segment is not
11: ; supported (the calls are commented out here) but will be in the future.
12: ; The form and placement of these calls is indicated here as a guide
13: ; to future usage.
14: ;
15: ; One thing to beware of: if you disable interrupts (CLI) they may be
16: ; re-enabled for you by the operating system. This will occur if you
17: ; generate a fault of some sort. The easiest example is a segment not
18: ; present fault. When the segment is loaded and your code starts to
19: ; execute the interrupts will be enabled. The solution is simple: don't
20: ; load any selectors within the CLI/STI code.
21: ;
22: ; Any other fault will cause your process to be booted (i.e. GP fault).
23: ;
24: .286p
25:
26: _TEXT2 SEGMENT BYTE PUBLIC 'CODE'
27: _TEXT2 ENDS
28: _DATA SEGMENT WORD PUBLIC 'DATA'
29: _DATA ENDS
30: CONST SEGMENT WORD PUBLIC 'CONST'
31: CONST ENDS
32: _BSS SEGMENT WORD PUBLIC 'BSS'
33: _BSS ENDS
34:
35: DGROUP GROUP CONST, _BSS, _DATA
36:
37: ; EXTRN DOSPORTACCESS:FAR
38:
39: ASSUME CS: _TEXT2, DS: DGROUP, SS: DGROUP, ES: DGROUP
40:
41: _TEXT2 SEGMENT
42:
43: PORT1 EQU 3D4h
44: PORT2 EQU 3D5h
45: CURSOR_H EQU 14 ; cursor location HIGH register
46: CURSOR_L EQU 15 ; cursor location LOW register
47: ACCESSREQ EQU 0 ; request access to port(s)
48: ACCESSREL EQU 1 ; release access to port(s)
49:
50: ;** _GetCurLoc - gets cursor location on the CRT screen
51: ;
52: ; ENTRY NONE
53: ;
54: ; EXIT (AX) = cursor location
55: ;
56: ; USES AX, BX, DX
57:
58: PUBLIC _GetCurLoc ; gets cursor location on CRT screen
59:
60: _GetCurLoc PROC FAR
61:
62: ; push 0 ; RESERVED WORD
63: ; push ACCESSREQ ; request access to port(s)
64: ; push PORT1
65: ; push PORT2
66: ; call DOSPORTACCESS ; request access to ports PORT1, PORT2
67:
68: mov ax,CURSOR_H ; address of register we want to read from
69: call ReadLoc ; gets cursor location (H) in AL
70: mov bh,al ; (BH) = cursor location (H)
71:
72: mov ax,CURSOR_L ; address of register we want to read from
73: call ReadLoc ; gets cursor location (L) in AL
74: mov ah,bh ; (AH) = cursor location (H)
75:
76: push ax ; save cursor location
77: ; push 0 ; RESERVED WORD
78: ; push ACCESSREL ; release access to port(s)
79: ; push PORT1
80: ; push PORT2
81: ; call DOSPORTACCESS ; release access to ports PORT1, PORT2
82: pop ax ; restore cursor location
83:
84: ret
85: _GetCurLoc ENDP
86:
87: ;* ReadLoc - reads cursor location on the CRT screen
88: ;
89: ; ENTRY (AX) = address of register to read from
90: ;
91: ; EXIT (AL) = cursor location read
92: ;
93: ; USES AX,DX
94:
95: ReadLoc PROC NEAR
96: cli
97: mov dx,PORT1 ; set address we want to output to
98: out dx,al
99: jmp $+2 ; PC/AT IO delay
100: mov dx,PORT2 ; set address we want to read from
101: in al,dx ; read cursor location
102: sti
103: ret
104: ReadLoc ENDP
105:
106: _TEXT2 ENDS
107:
108: END
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