.\"	$NetBSD: isv.4,v 1.7 2014/03/18 18:20:39 riastradh Exp $
.\"
.\" Copyright (c) 2008 The NetBSD Foundation, Inc.
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.\"
.\" This code is derived from software contributed to The NetBSD
.\" Foundation by David Young.
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.Dd April 1, 2008
.Dt ISV 4
.Os
.Sh NAME
.Nm isv
.Nd IDEC Supervision/16 image capture board
.Sh SYNOPSIS
.Cd "isv0 at isa? port 0x2f0"
.Cd "isv0 at isa? port 0x2e0"
.Cd "isv0 at isa? port 0x3f0"
.Cd "isv0 at isa? port 0x3e0"
.Sh DESCRIPTION
.Pp
.Nm
is a driver for the IDEC Supervision/16, an image capture board
that plugs into a 16-bit ISA bus.
The IDEC Supervision/16 digitizes an NTSC television signal, storing
a 512 x 480-pixel, 8-bit grayscale image in its 256kB dynamic RAM array
every 1/30th of a second.
The host reads frames from the DRAM using 122881 16-bit I/O reads.
Reading frames from the Supervision/16 is quite slow:
after the host reads a 16-bit word from the DRAM, the Supervision/16
state machine takes approximately 0.5 microseconds to get ready
for the next read.
Theoretically, a frame rate of approximately 10 frames per second
is possible.
.Nm
achieves a frame rate of approximately 6 frames per second.
.Sh SEE ALSO
.\".Xr isvctl 8
.Rs
.%R Programming the Supervision/16 Image Capture Board
.%Q IDEC
.%D circa 1991
.Re
.Sh HISTORY
The
.Nm
device first appeared in
.Nx 5.0 .
.Sh AUTHORS
The
.Nm
driver was written by
.An David Young Aq Mt dyoung@NetBSD.org .
.Sh BUGS
Synchronizing with the hardware and reading frames from it is very
CPU-intensive.
.Pp
.Nm
will not detect the capture board if it is not attached to an active
video source.
To force
.Nx
to detect the capture board at any time, re-scan the ISA bus using,
e.g.,
.Ic drvctl Fl r Ar isa0 .