User manual

Chapter 3 Software Overview
NI-DAQ User Manual for PC Compatibles 3-76 ni.com
buffer. This option imposes the restriction that the double-buffered digital
block output is halted when a partial block of data has been output. This
means that the data from the first call to
DIG_DB_Transfer
with a count
less than half the circular buffer size is the last data output by the device.
Notice, however, that enabling either of the double-buffered digital output
options causes an artificial split in the digital block buffer, requiring DMA
reprogramming at the end of each half buffer. For a group that is configured
for handshaking, such a split means that a pause in data transfer can occur
while NI-DAQ reprograms the DMA. For a group configured for pattern
generation, this split can cause glitches in the digital input or output
pattern (time lapses greater than the programmed period) during DMA
reprogramming. Therefore, you should enable these options only if
necessary. Both options can be enabled or disabled by the
DIG_DB_Config
function.
Note
EISA chaining is disabled if partial transfers of half buffers are enabled.
Counter/Timer Function Group
The Counter/Timer function group contains three sets of functions—
the General Purpose Counter/Timer (
GPCTR) functions, the Interval
Counter/Timer (
ICTR) functions, and the Counter/Timer (CTR) functions.
These sets of functions perform a variety of timing I/O and counter
operations such as event counting, period and frequency measurement,
and single-pulse and pulse-train generation. See your hardware user
manual to find out which operations are supported by your device.
Table 3-8 shows the sets of functions according to the devices they support.
Note
For TIO-based 45XX DSA devices, use only counters 0 and 1. Refer to the NI-DAQ
Function Reference Online Help or the device user manual for counter pinouts.
Table 3-8. Devices Supported by the GPCTR, ICTR,andCTR Functions
Functional Set
E-Series, 622X,660X,
671X,andDSADevices
516 Devices,
DAQCard-500/700, Lab and
1200 Devices, LPM Devices
PC-TIO-10
GPCTR
yes no no
ICTR
no yes no
CTR
no no yes