Using The Burst Protocol; Deciding The Pclk Signal Direction - National Instruments 653 Series User Manual

Chapter 2 Using Your NI 653X

Using the Burst Protocol

Note Feed external clocking signals into the PCLK pin for burst-mode handshaking and
into the REQ pin when performing pattern I/O.
For more information on LabVIEW VIs and NI-DAQ functions, consult the
Note
LabVIEW Help and the NI-DAQ Function Reference Help.
NI 653X User Manual
From the perspective of the NI 653X, the peripheral device requests
the transfer of data by signaling on the REQ line. The NI 653X
acknowledges it is ready to transfer data by signaling on the ACK line.
Use Table 3-1, Handshaking Protocol
handshaking protocol for your application. To select a protocol compatible
with your peripheral device, compare the handshaking sequence and state
machine diagrams for each protocol in the later sections of Chapter 3,
Timing Diagrams.
The burst protocol differs from all the other handshaking protocols in that
it is the only synchronous (clocked) protocol. In addition to ACK and REQ,
the NI 653X and peripheral device share a clock signal over the PCLK line.
Refer to Chapter 3, Timing
protocol.
If you want to acquire or generate patterns of every edge of a clock
signal, refer to the Generating and Receiving Digital Patterns and
Waveforms—Pattern I/O

Deciding the PCLK Signal Direction

The NI 653X can receive an external PCLK signal to control data transfers
or generate a PCLK signal using an internal 32-bit counter to output to the
peripheral device. By default, the NI 653X generates the PCLK signal for
input operations and receives an external PCLK signal for output
operations.
To set the direction of the PCLK signal:
• NI-DAQ C interface—Set the
in
Set_DAQ_Device_Info
• LabVIEW—Set the Clock Reverse Mode attribute to ON using the
DIO Parameter VI.
Characteristics, to select a
Diagrams, for more information about the burst
section.
ND_CLOCK_REVERSE_MODE
.
2-18
to
ND_ON
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