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91 lines
3.4 KiB
Plaintext
91 lines
3.4 KiB
Plaintext
CP/M V2.2
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Application Note 05, 2/20/82
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Improving the CTRL-S Function
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Copyright 1982 by Digital Research
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CP/M is a registered trademark of Digital Research.
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DDT and SID are trademarks of Digital Research.
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Compiled November 1982
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Applicable products and version numbers: CP/M V2.2
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Program: BDOS
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The CTRL-S function controls screen scrolling during CRT output.
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However, the system does not recognize CTRL-S if you type another
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character before it.
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In the following code segment procedures, addresses given are
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hexadecimal offsets from the base of the CP/M system. The CCP is
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usually located at 980H, but can be located at A00H if a two-sector
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boot is used.
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You can assemble the patch for your size memory system. The
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cpmbase equals the BDOS entry point address at locations 6 and 7 in
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the base page of memory minus 806H. You must change this entry point
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address when you load DDT or SID . Under DDT or SID, follow the
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jump at location 5 until you find an address with a least significant
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digit of 6. In the following example, the cpmbase is E506H-806H or
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DD00H.
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0005 JMP CD00
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CD00 JMP D3A4
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D3A4 XTHL
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D3A5 SHLD E452
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D3A8 XTHL
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D3A9 JMP E506
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Patch into the SYSGEN or MOVCPM image exactly as you would patch
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in a new version of your BIOS, using the DDT i command followed by
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the DDT r command. Use the same offset as your custom BIOS. The
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call at cpmbase + 950H should be cpmbase + 923H before installing the
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following code:
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cpmbase equ ?
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;
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;
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org cpmbase + 950h
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;
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call cpmbase + 92Ah
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end
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1
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CP/M V2.2 Application Note 05
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Or, you can install the above procedure directly into MOVCPM, if
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MOVCPM.COM is on your system disk. The patch is applied
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automatically to any size system that you build using MOVCPM.
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Make a back-up copy of MOVCPM.COM before using DDT to make the
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following changes:
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A>ddt movcpm.com
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DDT VERS 2.2
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NEXT PC
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2700 0100
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-l1350
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1350 CALL 0923
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1353 POP B
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1354 PUSH B
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. . .
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-a1350
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1350 call 92a
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1353 .
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-g0
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A>save 38 movcpm1.com
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Use the new program MOVCPM1.COM in place of MOVCPM.COM. Any
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CP/M system generated with MOVCPM1.COM has the improved CTRL-S
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function.
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Licensed users are granted the right to include these
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modifications in CP/M V2.2 software.
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