NAME
hco - write and read the high current output buffer
SYNOPSIS
#include <hco_p.h>
#incldue <stdio_p.h>
fd dopen(path)
char *path;
int dclose (fildes)
FD fildes;
int dread (fildes, output)
FD fildes;
unsigned *output;
int dwrite (fidles, output)
FD fildes;
unsigned *output;
int dioctl (fildes, cmd, arg)
FD fildes;
int cmd, arg;
DESCRIPTION
dopen
clears the 16 output bits and returns a file descriptor to be used to
read, write and close the device.
path
points to a string "dev/hco
X
" where
X
is the minor device number of the 16-bit output biffer, as specified
in the configuration.
dread
stores the current 16-bit digital output value in the address passed as
output
and returns 0.
dwrite
sets the 16 output bits to the value pointed to by
output
and returns 0.
dioctl
selectively sets and clears bits in the output buffer. If
cmd
is HO_SETB the bit specified by
arg
is set to 1. If
cmd
is HO_CLRB the bit specified by
arg
is set to 0.
arg
can range from 1 (high order bit) to 16 (low order bit).
dclose
clears the output bits and returns 0.
FILES
/dev/hcoX
path name for digital output
X.
SEE ALSO
obuf(3U)
DIAGNOSTICS
If
dopen
is invoked with an illegal minor device number, it returns -1.
If
dclose, dread, dwrite,
or
dioctl
are passed illegal descriptors, a value of -1 is returned. If
dioctl
is passed an illegal
cmd
argument, a value of -1 is returned. If
dioctl
is passed an
arg
that is not between 1 and 16 a value of -1 is returned.