.TH E1432_SET_SOURCE_SUM 3 E1432
.SH NAME
.nf
e1432_set_source_sum \- Enable or disable source sum input
e1432_get_source_sum \- Get current state of source sum input
.fi
.IX e1432_set_source_sum(3) 3
.IX e1432_get_source_sum(3) 3
.SH SYNOPSIS
.cS
SHORTSIZ16 e1432_set_source_sum(E1432ID hw, SHORTSIZ16 ID,
                                SHORTSIZ16 source_sum)
SHORTSIZ16 e1432_get_source_sum(E1432ID hw, SHORTSIZ16 ID,
                                SHORTSIZ16 *source_sum)
.cE
.SH DESCRIPTION
\fIe1432_set_source_sum\fR enables or disables the source sum input,
of a single channel or group of channels \fIID\fR, to the value given
in \fIsource_sum\fR.

\fIe1432_get_source_sum\fR returns the current status of the source
sum input, of a single channel or group of channels \fIID\fR, into a
memory location pointed to by \fIsource_sum\fR.

\fIhw\fR must be the result of a successful call to
\fIe1432_assign_channel_numbers\fR, and specifies the group of
hardware to talk to.

\fIID\fR is either the ID of a group of channels that was obtained with a
call to \fIe1432_create_channel_group\fR, or the ID of a single channel.

\fIsource_sum\fR specifies whether the sum input is enabled or not.
The valid values are \fBE1432_SOURCE_SUM_OFF\fR to disable the sum
input and \fBE1432_SOURCE_SUM_ON\fR to enable the sum input.  The
signal on the sum input is internally added to the output that the
source would otherwise be produced.

Obviously, this function is not useful when talking to input or tach
channels.  Only source channels have a constant-level output.
This function only works on the Option 1D4 single-channel source.

For the Option 1D4 single-channel source, the "source_sum" input is
shared with the "source_cola" output.  Only one of these two may be
enabled at any one time.  For prototype Option 1D4 sources only, one
of the two must be enabled at all times, and the default is for the
constant-level output to be enabled and the sum input to be disabled.
.SH "RESET VALUE"
After a reset, \fIsum\fR is set to \fBE1432_SOURCE_SUM_OFF\fR.
.SH "RETURN VALUE"
Return 0 if successful, a (negative) error number otherwise.
.SH "SEE ALSO"
.na
e1432_set_source_cola
.ad
