National Instruments 653X Manuale Utente

© National Instruments Corporation

The 653X device supports several different handshaking protocols to 
communicate with your peripheral device. The protocol you select will 
determine the timing of the ACK and REQ signals.

From the perspective of the 653X device, the peripheral device requests 
the transfer of data by signaling on the REQ line. The 653X device 
acknowledges it is ready to transfer data by signaling on the ACK line.

Use Table 3-1, 

, to select a 

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, 

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 653X and peripheral device share a clock signal over the PCLK line. 
See Chapter 3, 

, for more information about the burst 

protocol.

If you want to acquire or generate patterns of every edge of a clock 
signal, see the 

section.

Feed external clocking signals into the PCLK pin for burst-mode handshaking and 

into the REQ pin when performing pattern I/O.

The 653X device 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 653X device generates the 
PCLK signal for input operations and receives an external PCLK signal for 
output operations.