-
Notifications
You must be signed in to change notification settings - Fork 7
/
Copy pathVIDEOID.ASM
466 lines (344 loc) · 15 KB
/
VIDEOID.ASM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
TITLE 'Listing C-1'
NAME VideoID
PAGE 55,132
;
; Name: VideoID
;
; Function: Detects the presence of various video subsystems and associated
; monitors.
;
; Caller: Microsoft C:
;
; void VideoID(VIDstruct);
;
; struct
; {
; char VideoSubsystem;
; char Display;
; }
; *VIDstruct[2];
;
; Subsystem ID values:
; 0 = (none)
; 1 = MDA
; 2 = CGA
; 3 = EGA
; 4 = MCGA
; 5 = VGA
; 80h = HGC
; 81h = HGC+
; 82h = Hercules InColor
;
; Display types: 0 = (none)
; 1 = MDA-compatible monochrome
; 2 = CGA-compatible color
; 3 = EGA-compatible color
; 4 = PS/2-compatible monochrome
; 5 = PS/2-compatible color
;
;
; The values returned in VIDstruct[0].VideoSubsystem and
; VIDstruct[0].Display indicate the currently active subsystem.
;
;ARGpVID EQU word ptr [bp+4] ; stack frame addressing
; FAR calls only
ARGpVID EQU word ptr [bp+6] ; stack frame addressing
VIDstruct STRUC ; corresponds to C data structure
Video0Type DB ? ; first subsystem type
Display0Type DB ? ; display attached to first subsystem
Video1Type DB ? ; second subsystem type
Display1Type DB ? ; display attached to second subsystem
VIDstruct ENDS
Device0 EQU word ptr Video0Type[di]
Device1 EQU word ptr Video1Type[di]
MDA EQU 1 ; subsystem types
CGA EQU 2
EGA EQU 3
MCGA EQU 4
VGA EQU 5
HGC EQU 80h
HGCPlus EQU 81h
InColor EQU 82h
MDADisplay EQU 1 ; display types
CGADisplay EQU 2
EGAColorDisplay EQU 3
PS2MonoDisplay EQU 4
PS2ColorDisplay EQU 5
TRUE EQU 1
FALSE EQU 0
DGROUP GROUP _DATA
_TEXT SEGMENT byte public 'CODE'
ASSUME cs:_TEXT,ds:DGROUP
PUBLIC _VideoID
_VideoID PROC near
push bp ; preserve caller registers
mov bp,sp
push si
push di
; initialize the data structure that will contain the results
mov di,ARGpVID ; DS:DI -> start of data structure
mov Device0,0 ; zero these variables
mov Device1,0
; look for the various subsystems using the subroutines whose addresses are
; tabulated in TestSequence; each subroutine sets flags in TestSequence
; to indicate whether subsequent subroutines need to be called
mov byte ptr CGAflag,TRUE
mov byte ptr EGAflag,TRUE
mov byte ptr Monoflag,TRUE
mov cx,NumberOfTests
mov si,offset DGROUP:TestSequence
L01: lodsb ; AL := flag
test al,al
lodsw ; AX := subroutine address
jz L02 ; skip subroutine if flag is false
push si
push cx
call ax ; call subroutine to detect subsystem
pop cx
pop si
L02: loop L01
; determine which subsystem is active
call FindActive
pop di ; restore caller registers and return
pop si
mov sp,bp
pop bp
ret
_VideoID ENDP
;
; FindPS2
;
; This subroutine uses INT 10H function 1Ah to determine the video BIOS
; Display Combination Code (DCC) for each video subsystem present.
;
FindPS2 PROC near
mov ax,1A00h
int 10h ; call video BIOS for info
cmp al,1Ah
jne L13 ; exit if function not supported (i.e.,
; no MCGA or VGA in system)
; convert BIOS DCCs into specific subsystems & displays
mov cx,bx
xor bh,bh ; BX := DCC for active subsystem
or ch,ch
jz L11 ; jump if only one subsystem present
mov bl,ch ; BX := inactive DCC
add bx,bx
mov ax,[bx+offset DGROUP:DCCtable]
mov Device1,ax
mov bl,cl
xor bh,bh ; BX := active DCC
L11: add bx,bx
mov ax,[bx+offset DGROUP:DCCtable]
mov Device0,ax
; reset flags for subsystems that have been ruled out
mov byte ptr CGAflag,FALSE
mov byte ptr EGAflag,FALSE
mov byte ptr Monoflag,FALSE
lea bx,Video0Type[di] ; if the BIOS reported an MDA ...
cmp byte ptr [bx],MDA
je L12
lea bx,Video1Type[di]
cmp byte ptr [bx],MDA
jne L13
L12: mov word ptr [bx],0 ; ... Hercules can't be ruled out
mov byte ptr Monoflag,TRUE
L13: ret
FindPS2 ENDP
;
; FindEGA
;
; Look for an EGA. This is done by making a call to an EGA BIOS function
; which doesn't exist in the default (MDA, CGA) BIOS.
FindEGA PROC near ; Caller: AH = flags
; Returns: AH = flags
; Video0Type and
; Display0Type updated
mov bl,10h ; BL := 10h (return EGA info)
mov ah,12h ; AH := INT 10H function number
int 10h ; call EGA BIOS for info
; if EGA BIOS is present,
; BL <> 10H
; CL = switch setting
cmp bl,10h
je L22 ; jump if EGA BIOS not present
mov al,cl
shr al,1 ; AL := switches/2
mov bx,offset DGROUP:EGADisplays
xlat ; determine display type from switches
mov ah,al ; AH := display type
mov al,EGA ; AL := subystem type
call FoundDevice
cmp ah,MDADisplay
je L21 ; jump if EGA has a monochrome display
mov CGAflag,FALSE ; no CGA if EGA has color display
jmp short L22
L21: mov Monoflag,FALSE ; EGA has a mono display, so MDA and
; Hercules are ruled out
L22: ret
FindEGA ENDP
;
; FindCGA
;
; This is done by looking for the CGA's 6845 CRTC at I/O port 3D4H.
;
FindCGA PROC near ; Returns: VIDstruct updated
mov dx,3D4h ; DX := CRTC address port
call Find6845
jc L31 ; jump if not present
mov al,CGA
mov ah,CGADisplay
call FoundDevice
L31: ret
FindCGA ENDP
;
; FindMono
;
; This is done by looking for the MDA's 6845 CRTC at I/O port 3B4H. If
; a 6845 is found, the subroutine distinguishes between an MDA
; and a Hercules adapter by monitoring bit 7 of the CRT Status byte.
; This bit changes on Hercules adapters but does not change on an MDA.
;
; The various Hercules adapters are identified by bits 4 through 6 of
; the CRT Status value:
;
; 000b = HGC
; 001b = HGC+
; 101b = InColor card
;
FindMono PROC near ; Returns: VIDstruct updated
mov dx,3B4h ; DX := CRTC address port
call Find6845
jc L44 ; jump if not present
mov dl,0BAh ; DX := 3BAh (status port)
in al,dx
and al,80h
mov ah,al ; AH := bit 7 (vertical sync on HGC)
mov cx,8000h ; do this 32768 times
L41: in al,dx
and al,80h ; isolate bit 7
cmp ah,al
loope L41 ; wait for bit 7 to change
jne L42 ; if bit 7 changed, it's a Hercules
mov al,MDA ; if bit 7 didn't change, it's an MDA
mov ah,MDADisplay
call FoundDevice
jmp short L44
L42: in al,dx
mov dl,al ; DL := value from status port
mov ah,MDADisplay ; assume it's a monochrome display
mov al,HGC ; look for an HGC
and dl,01110000b ; mask off bits 4 thru 6
jz L43
mov al,HGCPlus ; look for an HGC+
cmp dl,00010000b
je L43 ; jump if it's an HGC+
mov al,InColor ; it's an InColor card
mov ah,EGAColorDisplay
L43: call FoundDevice
L44: ret
FindMono ENDP
;
; Find6845
;
; This routine detects the presence of the CRTC on a MDA, CGA or HGC.
; The technique is to write and read register 0Fh of the chip (cursor
; low). If the same value is read as written, assume the chip is
; present at the specified port addr.
;
Find6845 PROC near ; Caller: DX = port addr
; Returns: cf set if not present
mov al,0Fh
out dx,al ; select 6845 reg 0Fh (Cursor Low)
inc dx
in al,dx ; AL := current Cursor Low value
mov ah,al ; preserve in AH
mov al,66h ; AL := arbitrary value
out dx,al ; try to write to 6845
mov cx,100h
L51: loop L51 ; wait for 6845 to respond
in al,dx
xchg ah,al ; AH := returned value
; AL := original value
out dx,al ; restore original value
cmp ah,66h ; test whether 6845 responded
je L52 ; jump if it did (cf is reset)
stc ; set carry flag if no 6845 present
L52: ret
Find6845 ENDP
;
; FindActive
;
; This subroutine stores the currently active device as Device0. The
; current video mode determines which subsystem is active.
;
FindActive PROC near
cmp word ptr Device1,0
je L63 ; exit if only one subsystem
cmp Video0Type[di],4 ; exit if MCGA or VGA present
jge L63 ; (INT 10H function 1AH
cmp Video1Type[di],4 ; already did the work)
jge L63
mov ah,0Fh
int 10h ; AL := current BIOS video mode
and al,7
cmp al,7 ; jump if monochrome
je L61 ; (mode 7 or 0Fh)
cmp Display0Type[di],MDADisplay
jne L63 ; exit if Display0 is color
jmp short L62
L61: cmp Display0Type[di],MDADisplay
je L63 ; exit if Display0 is monochrome
L62: mov ax,Device0 ; make Device0 currently active
xchg ax,Device1
mov Device0,ax
L63: ret
FindActive ENDP
;
; FoundDevice
;
; This routine updates the list of subsystems.
;
FoundDevice PROC near ; Caller: AH = display #
; AL = subsystem #
; Destroys: BX
lea bx,Video0Type[di]
cmp byte ptr [bx],0
je L71 ; jump if 1st subsystem
lea bx,Video1Type[di] ; must be 2nd subsystem
L71: mov [bx],ax ; update list entry
ret
FoundDevice ENDP
_TEXT ENDS
_DATA SEGMENT word public 'DATA'
EGADisplays DB CGADisplay ; 0000b, 0001b (EGA switch values)
DB EGAColorDisplay ; 0010b, 0011b
DB MDADisplay ; 0100b, 0101b
DB CGADisplay ; 0110b, 0111b
DB EGAColorDisplay ; 1000b, 1001b
DB MDADisplay ; 1010b, 1011b
DCCtable DB 0,0 ; translate table for INT 10h func 1Ah
DB MDA,MDADisplay
DB CGA,CGADisplay
DB 0,0
DB EGA,EGAColorDisplay
DB EGA,MDADisplay
DB 0,0
DB VGA,PS2MonoDisplay
DB VGA,PS2ColorDisplay
DB 0,0
DB MCGA,EGAColorDisplay
DB MCGA,PS2MonoDisplay
DB MCGA,PS2ColorDisplay
TestSequence DB TRUE ; this list of flags and addresses
DW FindPS2 ; determines the order in which this
; program looks for the various
EGAflag DB ? ; subsystems
DW FindEGA
CGAflag DB ?
DW FindCGA
Monoflag DB ?
DW FindMono
NumberOfTests EQU ($-TestSequence)/3
_DATA ENDS
END