.TH E1432_SET_DECIMATION_OUTPUT 3 E1432
.SH NAME
.nf
e1432_set_decimation_output \- Set single or multi-pass filter output
e1432_get_decimation_output \- Get current state of filter output
.fi
.IX e1432_set_decimation_output(3) 3
.IX e1432_get_decimation_output(3) 3
.SH SYNOPSIS
.cS
SHORTSIZ16 e1432_set_decimation_output(E1432ID hw, SHORTSIZ16 ID,
                                       SHORTSIZ16 output)
SHORTSIZ16 e1432_get_decimation_output(E1432ID hw, SHORTSIZ16 ID,
                                       SHORTSIZ16 *output)
.cE
.SH DESCRIPTION
\fIe1432_set_decimation_output\fR sets the filter output, of a single
channel or group of channels \fIID\fR, to single or multi-pass, based
on the value given in \fIoutput\fR.

\fIe1432_get_decimation_output\fR returns the current status of the
filter output, of a single channel or group of channels \fIID\fR, into
a memory location pointed to by \fIoutput\fR.

This parameter is a "global" parameter.  It applies to an entire E1432
module rather than to one of its channels.  The \fIID\fR parameter is
used only to identify which module the function applies to, and all
channels in that module will report the same value for this parameter.

\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.

\fIoutput\fR selects the type of output from the digital filters.
The digital filters consist of a cascaded chain of sections, each
decimating the data stream by a factor of two and reducing its
bandwidth by a factor of two.

Using \fBE1432_ONEPASS\fR for this parameter selects the output of the
last filter in the chain.  This is the normal operating mode of the
filter.

Using \fBE1432_MULTIPASS\fR causes an output consisting of the time
multiplexed outputs of all cascaded filters equal to or narrower than
the programmed bandwidth.  This mode is useful when gathering data for
synchronous analysis, or octave measurements.

The E1431 Host Interface library, but not the E1432 Host Interface
library, allows an addition value for \fIoutput\fR which enables both
multi-pass and oversampled data.  For the E1432 Host Interface library,
this can be achieved by using \fBE1432_MULTIPASS\fR, and then calling
\fIe1432_set_decimation_oversample\fR to enable oversampled data.

This parameter may also be set with \fIe1432_set_decimation_filter\fR.

When in the multi-pass mode on an E1432, the data size must be one of
the 32-bit sizes (see \fIe1432_set_data_size\fR).  If the data size is
set to \fBE1432_DATA_SIZE_32_SERV\fR, then each data sample is tagged
with a 4 bit \fIpasscount\fR.  The passcount is placed over the least
significant data bits (bits 0 to 3) of the 32-bit data sample.  This
passcount can be used to decode which samples come from which span of
data.  On an E1433, you are not required to use the 32-bit data size
when in multi-pass mode, but generally multi-pass mode is only useful
when the data size is \fBE1432_DATA_SIZE_32_SERV\fR.

\fBNote:\fR On an E1432, when operating in multi-pass mode and
oversampled mode, the top span is limited to 10kHz and the number of
channels is limited to eight.  At spans below 10kHz the full 16
channels can be used.

.SH "RESET VALUE"
After a reset, \fIoutput\fR is set to \fBE1432_ONEPASS\fR.
.SH "RETURN VALUE"
Return 0 if successful, a (negative) error number otherwise.
.SH "SEE ALSO"
.na
e1432_set_data_size, e1432_set_decimation_oversample,
e1432_set_anti_alias_digital
.ad
