100 lines
3.7 KiB
Plaintext
100 lines
3.7 KiB
Plaintext
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I. Character Set Selection on VT220 Terminals
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==================================================
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name C0 GL C1 GR
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+---+ +-------------------+ +---+ +-------------------+
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|00h| | | |80h| | |
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range | | | | 20h .. 7fh | | | | | a0h .. ffh |
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|1fh| | | |9fh| | |
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+---+ +-------------------+ +---+ +-------------------+
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length 32 96 32 96
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/\
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SECOND /||\ "lock"- or "single"-shift one set of G0, G1, G2 or
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STEP || G3 into one of the "displayable" charactersets GL
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|| or GR. (escape) sequences are: SI, SO, ESC ~, ESC n,
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|| ESC }, ESC o, ESC |, ESC N and ESC O.
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+----+ +----+ +----+ +----+
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name | G0 | | G1 | | G2 | | G3 |
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length |(96)| |(96)| |(96)| |(96)|
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+----+ +----+ +----+ +----+
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/\
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/||\ designate a hard or a soft character set as
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|| one of G0, G1, G2 or G3, used escape sequences
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FIRST || are, ESC ( X, ESC ) X, ESC * X and ESC + X - where X is
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STEP || B for ascii, < for supplemental, 0 for special, A for
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|| british, 4 for dutch, C and 5 for finnish etc. etc. ...
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||
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+-----+ +------------+ +--------+ +-----------+ +------------+
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name |ascii| |supplemental| |special | | national | |downloadable|
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| | | graphics | |graphics| |replacement| |characterset|
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length | (96)| | (96)| | (96)| | (96)| | (96)|
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+-----+ +------------+ +--------+ +-----------+ +------------+
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\-------\ /----------/ norway/danish
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| dutch
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together, this is also finnish
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referred to as the french
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multinational character french canada
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set (power on default german
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on a dec vt220) italian
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spanish
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swedish
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swiss
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II. Emulating Character Set Selection
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=========================================
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MDA/HCG/CGA:
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just a partial emulation is done, because these boards don't allow
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downloadable charactersets. some characters simply don't display
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because they are not in the characterset roms on the video board.
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if you want to change the mapping, have a look at the default tables
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in pcvt_tbl.h.
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EGA/VGA:
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these cards have provisions for downloadable charactersets and so
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many vt220/vt320 charactersets are fully supported:
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- US Ascii
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- DEC Supplemental
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- DEC Special Graphic
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- DEC Technical
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- ISO Latin-1
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- Downloadable
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when the emulator is started, it behaves initially similar to
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the MDA/CGA/HCG method described above.
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when a second (special) characterset for a given screen resolution
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is loaded via the "loadfont" utility, the emulator detects this fact
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and uses from then on extended tables to access the second charset
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as an upper half 512 characterset in terms of ega/vga speak.
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from this time on, vt220 downloadable fonts are usable.
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the organization of this extended characterset is as follows:
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0x00 ... 0x1f C0 display function fonts
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0x20 ... 0x3f C1 display function fonts
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0x40 ... 0x9f fonts for DEC Supplemental, DEC Special
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Graphic, DEC Technical and ISO Latin-1
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0xa0 ... 0xff VT220 Downloadable Font
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the mapping between vt220 charactersets and the charactersets inside
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the ega/vga is done by tables found in the file pcvt_tbl.h.
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there is a MSDOS fonteditor called "EVAFONT" available on the
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SIMTEL-20 archive, which i used to edit the character sets in the
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distribution.
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