Hercules machine \ VOGONS

Hercules machine

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First post, by SoftCat

Posted on 2010-06-13, 15:10

SoftCat Offline

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Posts: 48
Joined: 2009-06-29, 09:22

Incorrect waiting for vertical retrace on hercules machine. Look code:
-------------------------------------------------
mov dx,3BAh
wait_0:
in al,dx
test al,8
jnz wait_0
wait_1:
in al,dx
test al,8
jz wait_1
-------------------------------------------------
Look hgc.zip
Test program: hs_h.com
Results:
hs_h.gif -- MS-DOS video
hs_h_dosbox.gif -- DOSBox video

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hgc.zip

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40.12 KiB

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235 downloads

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Fair use/fair dealing exception

Reply 1 of 3, by ripsaw8080

Posted on 2010-06-13, 16:31

ripsaw8080 Offline

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Posts: 5040
Joined: 2006-04-25, 23:24

103BA  R-  CRT status register (see #P0656)
2
3Bitfields for mono video adapter CRT status register:
4Bit(s)	Description	(Table P0656)
5 7	HGC: vertical sync pulse in progress
6 6-4	adapter identification
7	(MSD says) if bit 7 changes within 8000h reads then
8	    =000 adapter is Hercules or compatible
9	    =001 adapter is Hercules+
10	    =101 adapter is Hercules InColor
11	    else: adapter is unknown
12 6-4	=111 on MDA and some HGC clones
13 5-4	(mono EGA, mono ET4000) diagnose video display feedback
14	select from color plane enable
15 3	(MDA,HGC) pixel stream (0=currently black, 1=currently white)
16	(mono EGA, mono VGA) vertical retrace in progress
17 2-1	(MDA) reserved
18 2	(HGC, mono EGA) lightpen flipflop set
19	(mono ET4000) reserved (0)
20 1	(HGC) lightpen input stream (if set, current value to get from
21	  PORT 03B5h registers 10h-11h)
22	(mono ET4000) reserved (0)
23 0	horizontal drive enabled

Don't know if vsync is working for the hercules machine type; but from the docs I have, it appears bit 7 should be tested (i.e. "test al,80h")

Reply 2 of 3, by h-a-l-9000

Posted on 2010-06-13, 16:37

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Joined: 2005-02-23, 00:14

Bit 7 is the v-sync signal on hercules, not bit 3. Bit 3 is the video signal which is a bit much effort to emulate.

1+1=10

Reply 3 of 3, by SoftCat

Posted on 2010-06-13, 19:00

SoftCat Offline

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Posts: 48
Joined: 2009-06-29, 09:22

Thank you! On CGA, EGA, VGA and SVGA (all types) bit 3 is the v-sync signal.
In DOSBox 0.73 and earlier on hercules machine bit 3 is the v-sync signal too.

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