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Add support for 48x12 video mode on Challenger 1P. 

Tested on real C1P hardware.
This commit is contained in:
Jeff Tranter 2023-05-05 18:02:42 -04:00
parent a325c95652
commit 17706208e8
2 changed files with 29 additions and 0 deletions
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13
doc/osi.sgml
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@ -187,8 +187,21 @@ Currently the following extra screen configuration modules are implemented:
<itemize>
<item><tt>osic1p-screen-s3-32x28.o</tt>: 32 columns by 28 lines mode
for Briel Superboard ///</item>
<item><tt>osic1p-screen-c1p-48x12.s</tt>: 48 columns by 12 lines mode
for Challenger 1P</item>
</itemize>
On the Briel Superboard /// you enter 32 column mode by holding down
the BREAK key on powerup.
On the Challenger 1P you can enable 48 column mode by writing a 1 to
bit 0 of address &dollar;D800, and writing a 0 to go back to 24 column mode.
You can use code like the following to do this:
<tscreen><verb>
*(char*)0xd800 = 1; /* Switch to 48 column mode */
</verb></tscreen>
<sect>Limitations<p>
<sect1>stdio implementation<p>

16
libsrc/osic1p/extra/screen-c1p-48x12.s Normal file
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@ -0,0 +1,16 @@
;
; Implementation of screen-layout related functions for Challenger 1P in 48x12 mode.
;
.include "../osiscreen.inc"
C1P_SCR_BASE := $D000 ; Base of C1P video RAM
C1P_VRAM_SIZE = $0400 ; Size of C1P video RAM (1 kB)
C1P_SCR_WIDTH = $30 ; Screen width
C1P_SCR_HEIGHT = $0C ; Screen height
C1P_SCR_FIRSTCHAR = $8B ; Offset of cursor position (0, 0) from base
; of video RAM
C1P_SCROLL_DIST = $40 ; Memory distance for scrolling by one line
osi_screen_funcs C1P_SCR_BASE, C1P_VRAM_SIZE, C1P_SCR_FIRSTCHAR, \
C1P_SCR_WIDTH, C1P_SCR_HEIGHT, C1P_SCROLL_DIST