National Instruments DIO 6533 사용자 설명서

Chapter 4

Signal Connections

DIO 6533 User Manual

4-12

© National Instruments Corporation

For unstrobed operations, you have a choice of two types of output 
drivers: standard and wired-OR. A standard driver drives its output pin 
to approximately 0 V for logic low, or +5 V for logic high. A standard 
driver has several advantages:

•

It does not rely on pull-up resistors.

•

It is independent of the state of the DPULL line.

•

It has high current drive for both its logic high and logic low states.

•

It can drive high-speed transitions in both the high-to-low and 
low-to-high directions.

A wired-OR output driver drives its output pin to 0 V for logic low, but 
floats (tri-states) the pin for logic high. Therefore, a wired-OR output 
driver requires a pull-up resistor to pull the pin to +5 V for logic high. 
To provide a pull-up resistor, you can connect the DPULL pin on the 
I/O connector to the +5 V pin, making the 6533 device 100 k

Ω

 

pull-down resistors into 100 k

Ω

 pull-up resistors. A wired-OR driver 

has the following advantages over a standard driver:

•

You can connect two or more wired-OR outputs together without 
damaging the drivers.

•

You can connect wired-OR outputs to open-collector drivers, to 
GND signals, or to switches connecting to GND signals, without 
damaging the drivers.

•

You can use wired-OR outputs bidirectionally. For example, after 
connecting wired-OR outputs together, you can read back the value 
of one of the pins to determine whether any of the connected 
outputs is logic low.

Strobed operations, such as pattern generation and handshaking, use the 
same data signal connections as unstrobed operations, with the 
following exceptions:

•

You can configure data signals only on a port-by-port basis, rather 
than on a pin-by-pin basis. To configure data ports, you must assign 
them to handshaking groups.

•

Strobed output operations use only standard, rather than wired-OR, 
output drivers.