shithub: 9ferno

ref: 6966e8d72ae8fb72ebf98909acbd464aff84a3cc

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.TH VID 3 MPC823
.SH NAME
vid \- Motorola 823 video output
.SH SYNOPSIS
.B bind -b #v /dev
.PP
.B /dev/viddata
.br
.B /dev/vidctl
.br
.B /dev/vidcram
.SH DESCRIPTION
The
.I vid
device serves two
files giving basic access
to the on-chip video output of the Motorola 823.
It assumes a video hardware configuration exactly like that of the 823FADS
board, with an I²C interface to an off-chip ADV7176 NTSC/PAL converter
at I²C address 0x54.
.PP
The control device
.B vidctl
accepts the following commands:
.TP
.B on
Disable LCD panel (if present) and enable output from the video frame buffer.
.TP
.B off
Stop display from the video frame buffer and re-enable the LCD panel (if present).
.TP
.BI mode " m"
Set the video output format to
.IR m ,
which is one of:
.BR ntsc ,
.BR pal-i ,
.B pal-m
or
.BR pal-n .
This command is only effective when video output is off.
When next switched on, the both the video controller RAM and
ADV7176 are reprogrammed to the new format.
.PP
Video data can be written to the video frame buffer
by writes of the
.B viddata
file.
The file offset selects the starting byte within the frame buffer.
Reads return the corresponding data from the frame buffer.
The application is responsible for formatting the data as the 823's video
encoder requires, for the selected video format.
.PP
The file
.B vidcram
gives read and write access to the contents of the
video control RAM.
The file offset addresses bytes in the RAM; values can be read from or
written to the RAM in groups of 4-byte big-endian words.
.SH SOURCE
.B /os/mpc/devvid.c
.SH BUGS
Square pixel mode cannot be used on the FADS board:
no suitable video clock source is available.