NI 6528 User manual

USER GUIDE AND SPECIFICATIONS
NI 6528/6529
The NI PCI/PXI-6528 device provides 24 isolated input channels and
24 isolated output channels, and the NI PXI-6529 provides 48 isolated
input channels. The NI 6528/6529 features digital filtering, change
detection, and Real-Time System Integration (RTSI) capabilities. The
NI 6528 also features programmable power-up output states and a
watchdog timer. The NI 6528/6529 is ideal for high-voltage isolation
and switching in both industrial and laboratory environments.
Contents
Configuration .......................................................................................... 2
Programming Devices in Software .................................................. 3
Functional Overview............................................................................... 4
Safety Information .................................................................................. 5
Related Documentation........................................................................... 7
Features ................................................................................................... 8
Digital Filtering................................................................................ 8
Digital Filtering Example ......................................................... 9
RTSI................................................................................................. 9
Change Detection............................................................................. 10
Change Detection and RTSI ..................................................... 10
Change Detection Example ...................................................... 11
Programmable Power-Up Output States (NI 6528 Only) ................ 11
Watchdog Timer (NI 6528 Only) .................................................... 12
Watchdog Timer and RTSI....................................................... 12
Digital I/O ............................................................................................... 13
I/O Connector .................................................................................. 13
Pin Assignments .............................................................................. 13
Signal Descriptions .......................................................................... 15
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NI 6528/6529 User Guide and Specifications 2 ni.com
Optically Isolated Inputs...................................................................16
Sensing DC Voltages ................................................................16
Signal Connection Example......................................................17
Solid-State Relay Outputs (NI 6528 Only) ......................................18
Using the NI 6528 as a TTL-Level Device...............................19
Maximum Power Ratings..........................................................20
Power-On and Power-Off Conditions.......................................20
Power Connections ..................................................................................20
Isolation Circuitry.............................................................................21
Isolation Voltages.............................................................................21
Protecting Inductive Loads (NI 6528 Only).....................................21
Accessories ..............................................................................................22
Specifications...........................................................................................23
Configuration
The NI 6528/6529 device is completely software configurable, so it is not
necessary to set jumpers for I/O configuration.
The PCI-6528 device is fully compliant with the PCI Local Bus
Specification, Revision 2.2, and the PXI-6528/6529 device is fully
compliant with the PXI Hardware Specification, Revision 2.1. The
PCI/PXI system automatically allocates all device resources, including the
base address and interrupt level. The device base address is mapped into
PCI memory space. It is not necessary to perform configuration steps after
the system powers up.
Refer to the application software documentation for configuration
instructions.
After the NI 6528/6529 device and the software are installed, the DAQ
device appears under the Devices and Interfaces branch of the
Measurement & Automation Explorer (MAX) configuration tree.
If the DAQ device does not appear in MAX, use the following
troubleshooting guidelines.
• Verify that you are using the correct version of NI-DAQ (NI-DAQ 7.1
or later for the NI 6528, and NI-DAQ 8.6 or later for the NI 6529).
To download the most recent National Instruments drivers, go to
ni.com/drivers.
• Press <F5> to refresh the MAX window, or close and re-open MAX.
• Restart the computer.
• Power off and unplug the computer or chassis, and install the device in
a different slot. Refer to the DAQ Getting Started guides for
installation instructions and safety guidelines.

©National Instruments Corporation 3 NI 6528/6529 User Guide and Specifications
• NI PCI-6528 devices must be installed into a slot that provides 3.3 V.
Check that the 3.3 V LED (reference designator DS1—located on the
visible edge of the underside of the installed device) is lit. If not, check
that the PC motherboard provides 3.3 V to the PCI bus.
Programming Devices in Software
National Instruments measurement devices are packaged with NI-DAQ
driver software, an extensive library of functions and VIs you can call from
your application software, such as LabVIEW or LabWindows™/CVI™, to
program all the features of your NI measurement devices. Driver software
has an application programming interface (API), which is a library of VIs,
functions, classes, attributes, and properties for creating applications for
your device.
NI-DAQ 8.xor later includes two NI-DAQ drivers, Traditional NI-DAQ
(Legacy) and NI-DAQmx. Each driver has its own API, hardware
configuration, and software configuration. Refer to the DAQ Getting
Started guides for more information about the two drivers.
Traditional NI-DAQ (Legacy) and NI-DAQmx each include a collection of
programming examples to help you get started developing an application.
You can modify example code and save it in an application. You can use
examples to develop a new application or add example code to an existing
application.
To locate LabVIEW and LabWindows/CVI examples, open the National
Instruments Example Finder:
• In LabVIEW, select Help»Find Examples.
• In LabWindows/CVI, select Help»NI Example Finder.
Measurement Studio, Visual Basic, and ANSI C examples are in the
following directories:
• NI-DAQmx examples for Measurement Studio-supported languages
are in the following directories:
–MeasurementStudio\VCNET\Examples\NIDaq
–MeasurementStudio\DotNET\Examples\NIDaq
• Traditional NI-DAQ (Legacy) examples for Visual Basic are in the
following two directories:
–NI-DAQ\Examples\Visual Basic with Measurement
Studio directory contains a link to the ActiveX control examples
for use with Measurement Studio
–NI-DAQ\Examples\VBasic directory contains the examples not
associated with Measurement Studio

NI 6528/6529 User Guide and Specifications 4 ni.com
• NI-DAQmx examples for ANSI C are in the
NI-DAQ\Examples\DAQmx ANSI C Dev directory
• Traditional NI-DAQ (Legacy) examples for ANSI C are in the
NI-DAQ\Examples\VisualC directory
For additional examples, refer to zone.ni.com.
Functional Overview
Figures 1 and 2 illustrate the key functional components of the
NI 6528/6529 device.
Figure 1. NI 6528 Block Diagram
PCI Bus
Interface
Flash
Memory
Configuration
Control
Data/Control Data/Control
24 Outputs 24 Outputs
Output Buffers
and Isolation
Input
Isolation
24 Inputs 24 Inputs
Industrial Digital
I/O Control FPGA
DIO Lines
Programmable
Power-Up States
Watchdog Timer
Change
Detection
Digital
Filtering
RTSI
PCI/PXI/CompactPCI Bus
I/O Connector
10 MHz
Clock
RTSI
RTSI

©National Instruments Corporation 5 NI 6528/6529 User Guide and Specifications
Figure 2. NI 6529 Block Diagram
Safety Information
The following section contains important safety information that you must
follow when installing and using National Instruments DIO devices.
Do not operate the device in a manner not specified in this document.
Misuse of the DIO device can result in a hazard. You can compromise the
safety protection built into the DIO device if it is damaged in any way. If
the DIO device is damaged, return it to National Instruments for repair.
Do not substitute parts or modify the DIO device except as described in this
document. Use the DIO device only with the chassis, modules, accessories,
and cables specified in the installation instructions. You must have all
covers and filler panels installed during operation of the DIO device.
Do not operate the DIO device in an explosive atmosphere or where there
may be flammable gases or fumes. If you must operate the DIO device in
such an environment, it must be in a suitably rated enclosure.
If you need to clean the DIO device, use a soft, nonmetallic brush. Make
sure that the DIO device is completely dry and free from contaminants
before returning it to service.
PCI Bus
Interface
Flash
Memory
Configuration
Control
Data/Control Data/Control
Input
Isolation
48 Inputs 48 Inputs
Industrial Digital
I/O Control FPGA
DI Lines
Change
Detection
Digital
Filtering
RTSI
PCI/PXI/CompactPCI Bus
I/O Connector
10 MHz
Clock
RTSI
RTSI

NI 6528/6529 User Guide and Specifications 6 ni.com
Operate the DIO device only at or below Pollution Degree 2. Pollution is
foreign matter in a solid, liquid, or gaseous state that can reduce dielectric
strength or surface resistivity. The following is a description of pollution
degrees:
• Pollution Degree 1 means no pollution or only dry, nonconductive
pollution occurs. The pollution has no influence.
• Pollution Degree 2 means that only nonconductive pollution occurs in
most cases. Occasionally, however, a temporary conductivity caused
by condensation must be expected.
• Pollution Degree 3 means that conductive pollution occurs, or dry,
nonconductive pollution occurs that becomes conductive due to
condensation.
You must insulate signal connections for the maximum voltage for which
the DIO device is rated. Do not exceed the maximum ratings for the DIO
device. Do not install wiring while the DIO device is live with electrical
signals. Do not remove or add connector blocks when power is connected
to the system. Avoid contact between your body and the connector block
signal when hot swapping modules. Remove power from signal lines
before connecting them to or disconnecting them from the DIO device.
Operate the DIO device at or below the measurement category1marked on
the hardware label. Measurement circuits are subjected to working
voltages2and transient stresses (overvoltage) from the circuit to which they
are connected during measurement or test. Installation categories establish
standard impulse withstand voltage levels that commonly occur in
electrical distribution systems. The following is a description of
measurement categories:
• Measurement Category I is for measurements performed on circuits
not directly connected to the electrical distribution system referred to
as MAINS3voltage. This category is for measurements of voltages
from specially protected secondary circuits. Such voltage
measurements include signal levels, special equipment, limited-energy
parts of equipment, circuits powered by regulated low-voltage sources,
and electronics.
1 Measurement categories, also referred to as installation categories, are defined in electrical safety standard IEC 61010-1.
2 Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular insulation.
3 MAINS is defined as a hazardous live electrical supply system that powers equipment. Suitably rated measuring circuits may
be connected to the MAINS for measuring purposes.

©National Instruments Corporation 7 NI 6528/6529 User Guide and Specifications
• Measurement Category II is for measurements performed on circuits
directly connected to the electrical distribution system. This category
refers to local-level electrical distribution, such as that provided by a
standard wall outlet (for example, 115 V for U.S. or 230 V for Europe).
Examples of Measurement Category II are measurements performed
on household appliances, portable tools, and similar DIO devices.
• Measurement Category III is for measurements performed in the
building installation at the distribution level. This category refers to
measurements on hard-wired equipment such as equipment in fixed
installations, distribution boards, and circuit breakers. Other examples
are wiring, including cables, bus-bars, junction boxes, switches,
socket-outlets in the fixed installation, and stationary motors with
permanent connections to fixed installations.
• Measurement Category IV is for measurements performed at the
primary electrical supply installation (<1,000 V). Examples include
electricity meters and measurements on primary overcurrent
protection devices and on ripple control units.
Related Documentation
The following documents contain information that you may find helpful as
you use this user guide:
•DAQ Getting Started guides—These guides describes how to install
the NI-DAQ software, the DAQ device, and how to confirm that the
device is operating properly.
•NI-DAQmx Help—This help file contains information about using
NI-DAQmx to program National Instruments devices. NI-DAQmx
is the software you use to communicate with and control NI DAQ
devices.
•Measurement & Automation Explorer Help for NI-DAQmx—This
help file contains information about configuring and testing DAQ
devices using Measurement & Automation Explorer (MAX) for
NI-DAQmx, and information about special considerations for
operating systems.
•DAQ Assistant Help—This help file contains information about
creating and configuring channels, tasks, and scales using the
DAQ Assistant.
Note You can download these documents from ni.com/manuals.

NI 6528/6529 User Guide and Specifications 8 ni.com
Features
The NI 6528/6529 features digital filtering, Real-Time System Integration
(RTSI), and change detection. The NI 6528 also features programmable
power-up output states and a watchdog timer.
Digital Filtering
Use the digital filter option available on the NI 6528/6529 input lines to
eliminate glitches on input data. When used with change detection, filtering
can also reduce the number of changes to examine and process.
You can configure the digital input channels to pass through a digital filter,
and you can program the filter interval the filter uses. The filter blocks
pulses that are shorter than half of the specified filter interval and passes
pulses that are longer than the specified interval. Intermediate-length
pulses—pulses longer than half of the interval but less than the
interval—may or may not pass the filter.
The filter operates on the inputs from the optocouplers. The optocouplers
turn on faster than they turn off, passing rising edges faster than falling
edges. The optocouplers can therefore subtract up to 150 s from a low
pulse.
Table 1 lists the pulse widths guaranteed to be passed and blocked.
You can enable filtering on as many input lines as is necessary for your
application. All filtered lines share the same timing interval, which ranges
from 400 ns to 200 ms.
Internally, the filter uses two clocks: the sample clock and the filter clock.
The sample clock has a 100 ns period. The filter clock is generated by a
counter and has a period equal to one half of the specified timing interval.
The input signal is sampled on each rising edge of the sample clock, which
is every 100 ns. A change in the input signal is recognized only if it
maintains its new state for at least two consecutive rising edges of the filter
clock.
Table 1. NI 6528/6529 Digital Filtering
Filter Interval
Pulse Width Passed Pulse Width Blocked
Low Pulse High Pulse Low Pulse High Pulse
tinterval tinterval + 150 s tinterval tinterval/2 (tinterval/2) – 150 s

©National Instruments Corporation 9 NI 6528/6529 User Guide and Specifications
The filter clock is programmable and allows you to control how long a
pulse must last to be recognized. The sample clock provides a fast sample
rate to ensure that input pulses remain constant between filter clocks.
Digital Filtering Example
Figure 3 shows a filter configuration with a tinterval filter interval
(tinterval/2 filter clock).
Figure 3. Digital Filtering Example
In periods A and B, the filter blocks the glitches because the external signal
does not remain steadily high from one rising edge of the filter clock to the
next. In period C, the filter passes the transition because the external signal
remains steadily high. Depending on when the transition occurs, the filter
may require up to two filter clocks—one full filter interval—to pass a
transition. The figure shows a rising (0 to 1) transition. The same filtering
applies to falling (1 to 0) transitions.
RTSI
The NI 6528/6529 uses the National Instruments Real-Time System
Integration (RTSI) bus interface to route additional timing and trigger
signals between the NI 6528/6529 and National Instruments
RTSI-compatible devices. Use the National Instruments RTSI cable to
connect the NI PCI-6528 to other RTSI-compatible devices.
The NI PXI-6528/6529 uses pins on the RTSI connector to connect the
RTSI bus to the PXI trigger bus, as defined in the PXI Hardware
Specification, Revision 2.1. The NI PCI-6528 uses pins on the RTSI
connector to connect the RTSI bus to the PCI trigger bus, as defined in the
PCI Local Bus Specification, Revision 2.2. All National Instruments
PCI/PXI devices that have a connection to these pins can be connected
through software. This feature is not supported by CompactPCI.
HHHHH
HLLHH
HLLHH
A
B
C
Sample Clock
External
Signal
Sampled
Filtered
Signal
External
Signal
Filter
Clock

NI 6528/6529 User Guide and Specifications 10 ni.com
The NI 6528 has eight lines that are configurable for either input or output,
and the NI PXI-6528 has a PXI star trigger line in addition to these
eight I/O lines. The NI PXI-6529 has eight lines for output and a PXI star
trigger line.
Note The PXI star trigger is for input only.
Input Port 0 can be configured to route signals to the RTSI port.
Output Port 3 can be configured to route signals from the RTSI port.
Additionally, on the NI PXI-6528/6529, the PXI star trigger line can be
configured to be routed to line 0 of output Port 4.
Refer to the Change Detection and RTSI and Watchdog Timer and RTSI
sections for more information about using the NI 6528/6529 with RTSI.
Change Detection
You can program the NI 6528/6529 to send an interrupt when a change
occurs on any input line.
The NI 6528/6529 can monitor changes on selected input lines or on all
input lines. It can monitor for rising edges (0 to 1), falling edges (1 to 0),
or both. When an input change occurs, the NI 6528/6529 generates an
interrupt, and the NI-DAQ driver then notifies the software.
Note Excessive change detections can affect system performance. Use digital filtering to
minimize the effects of noisy input lines.
The NI 6528/6529 sends a change detection when any one of the changes
occurs, but it does not report which line changed or if the line was rising or
falling. After a change, you can read the input lines to determine the current
line states. The maximum rate of change detection is determined by the
software response time, which varies from system to system.
An overflow bit indicates that an additional rising or falling edge has been
detected before the software could process the previous change.
Refer to the software documentation for information about how to set up
and implement the change detection.
Change Detection and RTSI
You can program the NI 6528/6529 to send a 200 ns pulse to any or all
RTSI lines when a change is detected. The pulse generates when a change
detection event occurs.

©National Instruments Corporation 11 NI 6528/6529 User Guide and Specifications
Change Detection Example
Table 2 shows a change detection example for six bits of one port.
This example assumes the following line connections:
• Bits 7, 6, 5, and 4 are connected to data lines from a four-bit TTL
output device. The NI 6528/6529 detects any change in the input data
so you can read the new data value.
• Bit 1 is connected to a limit sensor. The NI 6528/6529 detects rising
edges on the sensor, which correspond to over-limit conditions.
• Bit 0 is connected to a switch. The software can react to any switch
closure, which is represented by a falling edge. If the switch closure is
noisy, enable digital filtering for this line.
In this example, the NI 6528/6529 reports rising edges only on bit 1, falling
edges only on bit 0, and rising and falling edges on bits 7, 6, 5, and 4. The
NI 6528/6529 reports no changes for bits 3 and 2. After receiving
notification of a change, you can read the port to determine the current
values of all eight lines. You cannot read the state of any lines that are
configured for change detection until the change detection interrupt occurs.
Programmable Power-Up Output States (NI 6528 Only)
The default power-up state of the digital output lines is logic high, which
opens the solid-state relays. The lines on output ports are user-configurable
for logic high (open relay) or logic low (closed relay). User-configurable
power-up states are useful for ensuring that the NI 6528 powers up in a
known state.
Table 2. Change Detection Example
Bit
7 6 5 4 3 2 1 0
Changes to detect — —
Enable rising-edge
detection
yes yes yes yes no no yes no
Enable falling-edge
detection
yes yes yes yes no no no yes

NI 6528/6529 User Guide and Specifications 12 ni.com
To use MAX (recommended) to program the power-up states, select
the device and click the Properties button. Refer to the software
documentation for information about how to program the power-up states
using NI-DAQ with LabVIEW or other National Instruments application
development environments (ADEs).
Note The response time of programmable power-up states is 400 ms.
Watchdog Timer (NI 6528 Only)
The watchdog timer is a software configurable feature used to set critical
outputs to safe states in the event of a software failure, a system crash, or
any other loss of communication between the application and the NI 6528.
When the watchdog timer is enabled, if the NI 6528 does not receive a
watchdog reset software command within the time specified for the
watchdog timer, the outputs go to a user-defined safe state and remain in
that state until the watchdog timer is disarmed by the application and new
values are written, the NI 6528 is reset, or the computer is restarted. The
expiration signal that indicates an expired watchdog will continue to assert
until the watchdog is disarmed. After the watchdog timer expires, the
NI 6528 ignores any writes until the watchdog timer is disarmed.
You can set the watchdog timer timeout period to specify the amount of
time that must elapse before the watchdog timer expires. The counter on the
watchdog timer is configurable up to (232 – 1) × 100 ns (approximately
seven minutes) before it expires.
Watchdog Timer and RTSI
Using the watchdog timer and RTSI, you can chain multiple NI 6528
devices and configure them to expire simultaneously while updating only
one timer.
You can program the NI 6528 to send a 200 ns logic high pulse to any or
all RTSI lines when the watchdog timer expires. Additionally, you can
program the watchdog timer to expire when it detects either a rising or a
falling edge on a single RTSI line.

©National Instruments Corporation 13 NI 6528/6529 User Guide and Specifications
Digital I/O
The I/O connector, device pinout, signal descriptions, optically isolated
inputs, and solid-state relay (SSR) outputs are discussed in this section.
I/O Connector
The 100-pin high-density SCSI connector provides access to 24 digital
inputs and 24 digital outputs on the NI 6528 and to 48 digital inputs on the
NI 6529. For easy connection to the I/O connector, use the National
Instruments SH100-100-F shielded cable with the SCB-100 connector
block, or use the R1005050 cable with the CB-50 or CB-50LP connector
block.
Caution Do not make connections to the digital I/O that exceed the maximum I/O
specifications. Doing so may permanently damage the NI 6528/6529 device and the
chassis. Refer to the Signal Descriptions section and the Specifications section for
information about maximum input ratings.
Refer to the Pin Assignments section for the NI 6528/6529 I/O connector
pinout.
Pin Assignments
Figure 4 shows the pin assignments for the 100-pin connector on the
NI 6528/6529 device.
The naming convention for each pin is PX.Y, where Xis the port (P) number,
Yis the line number, and a + or – indicates whether the terminal is positive
or negative.
Note For input ports on the NI 6528/6529, connect the higher voltage to the PX.Y+ pin and
the lower voltage to the PX.Y– pin. For output ports on the NI 6528, you can connect signals
to the two pins of each line, regardless of which has the higher voltage. The output lines on
the NI 6528 are solid-state relays and act as bi-directional switches.

NI 6528/6529 User Guide and Specifications 14 ni.com
Figure 4. NI 6528/6529 Pinout
NI 6528 (Pins1–48) Direction Input—Ports0, 1, and 2
(Pins51–98) Direction Output with Readback—Ports3, 4, and 5
NI 6529 (Pins1–48, 51–98) Direction Input—Ports0 through 5
GND
+5 V
P0.0–
P0.0+
P0.1–
P0.1+
P0.2–
P0.2+
P0.3–
P0.3+
P0.4–
P0.4+
P0.5–
P0.5+
P0.6–
P0.6+
P0.7–
P0.7+
P1.0–
P1.0+
P1.1–
P1.1+
P1.2–
P1.2+
P1.3–
P1.3+
P1.4–
P1.4+
P1.5–
P1.5+
P1.6–
P1.6+
P1.7–
P1.7+
P2.0–
P2.0+
P2.1–
P2.1+
P2.2–
P2.2+
P2.3–
P2.3+
P2.4–
P2.4+
P2.5–
P2.5+
P2.6–
P2.6+
P2.7–
P2.7+
GND
+5 V
P3.0–
P3.0+
P3.1–
P3.1+
P3.2–
P3.2+
P3.3–
P3.3+
P3.4–
P3.4+
P3.5–
P3.5+
P3.6–
P3.6+
P3.7–
P3.7+
P4.0–
P4.0+
P4.1–
P4.1+
P4.2–
P4.2+
P4.3–
P4.3+
P4.4–
P4.4+
P4.5–
P4.5+
P4.6–
P4.6+
P4.7–
P4.7+
P5.0–
P5.0+
P5.1–
P5.1+
P5.2–
P5.2+
P5.3–
P5.3+
P5.4–
P5.4+
P5.5–
P5.5+
P5.6–
P5.6+
P5.7–
P5.7+
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76

©National Instruments Corporation 15 NI 6528/6529 User Guide and Specifications
Refer to the Signal Descriptions section for information about the signals
available on this connector.
Signal Descriptions
Table 3 and Table 4 list the signals and descriptions for all signals available
on the NI 6528/6529 devices.
Table 3. NI 6528 Signal Descriptions
Signal Name Direction Description
P<0..2>.<7..0>+ Input Isolated input ports <0..2>, positive terminals—Take
measurements at these terminals. A logic high (data bit of 1)
indicates sufficient input voltage and current are present.
P<0..2>.<7..0>– Input Isolated input ports <0..2>, negative terminals—Each of these
terminals serves as the reference terminal from which the
corresponding P line is measured.
+5 V Output +5 Volts—Provides +5 VDC power. These pins are not isolated.
GND —Ground—These pins are connected to the computer ground
reference. These pins are not isolated.
P<3..5>.<7..0>+ Output Isolated output ports <3..5>, first terminals—Each of these is
the first of two terminals of a bi-directional solid-state relay. The
connection is complete when the relay is closed. The connection
is broken when the relay is open. A logic low (data bit of 0) closes
the relay.
P<3..5>.<7..0>– Output Isolated output ports <3..5>, second terminals—Each of these
is the second of two terminals of a bi-directional solid-state relay.
A logic low (data bit of 0) closes the relay.

NI 6528/6529 User Guide and Specifications 16 ni.com
Optically Isolated Inputs
Pins 1 through 48 on the NI 6528 and pins 1 through 48 and 51 through 98
on the NI 6529 are optically isolated input signal pins. These inputs consist
of a light-emitting diode (LED), a depletion-mode MOSFET-based current
limiting circuit, and digital filtering and change-detection circuitry.
The NI 6528 device provides 24 channels of isolated digital input, and the
NI 6529 device provides 48 channels of isolated digital input. Each channel
has its own positive and negative terminals. The input (VIN) range on the
channels is –60 VDC to +60 VDC.
Sensing DC Voltages
The NI 6528/6529 detects a wide range of DC signals, from TTL-like logic
levels to DC power supply levels up to 60 V.
Applying a DC voltage of at least 3.2 V across two input terminals registers
a logic high. Applying no voltage or a voltage difference of 1 V or less
registers as a logic low. DC voltages between 1 V and 3.2 V may not
register a consistent or usable value.
Table 4. NI 6529 Signal Descriptions
Signal Name Direction Description
P<0..5>.<7..0>+ Input Isolated input port <0..5>, positive terminals—Take
measurements at these terminals. A logic high (data bit of 1)
indicates sufficient input voltage and current are present.
P<0..5>.<7..0>– Input Isolated input port <0..5>, negative terminals—Each of these
terminals serves as the reference terminal from which the
corresponding P line is measured.
+5 V Output +5 Volts—Provides +5 VDC power. These pins are not isolated.
GND —Ground—These pins are connected to the computer ground
reference. These pins are not isolated.

©National Instruments Corporation 17 NI 6528/6529 User Guide and Specifications
Signal Connection Example
Figure 5 shows signal connections for a supply and load connected to an
isolated input.
Figure 5. Signal Connection Example
In the figure, the NI 6528/6529 device is sensing a powered load that is
connected to the power supply through a switch.
Note Power supplies must be within the NI 6528/6529 device range. Refer to the
Specifications section for information about these ranges.
When the switch is open, no current flows through the load and no voltage
is applied to the load or to the NI 6528/6529 device input. The digital logic
of the NI 6528/6529 device then registers a logic low for the channel.
When the switch is closed, current flows through both the load and the
NI 6528/6529 device input LED, and the NI 6528/6529 device registers a
logic high for the channel.
Load
PX.Y+
PX.Y–
3.3V
4.7 kΩ
Isolation Isolated Ground
Digital
Logic
Computer
Ground
NI 6528/6529
ILD217
Schottky
Supply
+
_
MOSFET-Based
Current-Limiting
Circuitry

NI 6528/6529 User Guide and Specifications 18 ni.com
Solid-State Relay Outputs (NI 6528 Only)
The solid-state relay (SSR) output channels on the NI 6528 device consist
of an LED and two MOSFETs that are connected to form a bi-directional
switch. Depending on how the load is connected to the terminals, an output
can either source or sink current.
Figures 6 and 7 show examples of sinking and sourcing current.
Figure 6. Sinking Current Connection Example
Figure 7. Sourcing Current Connection Example
PX.Y+
PX.Y–
LAA125
Isolated Ground
Supply
+
_
IF
VCC
Isolation
Digital
Logic
RS
18 Ω
NI 6528
Load
PX.Y+
PX.Y–
LAA125
Isolated
Ground
Supply
+
_
IF
VCC
Isolation
Digital
Logic
RS
18 Ω
NI 6528
Load

©National Instruments Corporation 19 NI 6528/6529 User Guide and Specifications
Using the NI 6528 as a TTL-Level Device
Using the +5 V line from the NI 6528 device allows you to use it as a
TTL-level output device with non-isolated power.
Figure 8 shows a signal connection example for both sinking and sourcing
current. This example shows a TTL-level application with a supply voltage
of +5 V.
Figure 8. TTL-Level Device Connection Example
When the SSR is open, a small amount of current flows through RLand the
output voltage is close to 5 V, a logic high. When the SSR is closed, current
flows through RLand the output voltage is close to 0 V, a logic low.
If isolation is not a concern, you can use the +5 V line from the NI 6528
device in place of the external +5 V supply.
Choose an RLvalue small enough to provide the necessary source current
but large enough to reduce sink current and to avoid consuming
unnecessary power. Many TTL-level applications use an RLvalue of 5 k.
VOUT
+5 V
Isolation Isolated Ground
Digital
Logic
RL= 5 kΩ
To External
+5 V Supply
18 Ω
NI 6528

NI 6528/6529 User Guide and Specifications 20 ni.com
Maximum Power Ratings
Table 5 lists the maximum power ratings for the output channels.
Power-On and Power-Off Conditions
The default power-on state of the digital output lines is logic high with the
solid-state relays open. By default, the solid-state relays remain open when
the computer and the NI 6528 device are powered off.
Refer to the Programmable Power-Up Output States (NI 6528 Only)
section for more information about power-on conditions.
Power Connections
Pins 50, 100, 49, and 99 on the I/O connector are not isolated. Pins 50 and
100 connect to GND, the computer ground reference. Pins 49 and 99 of the
I/O connector supply +5 V from the computer power supply. The I/O
connector power has a fuse for overcurrent protection. This fuse is not
customer replaceable. If the fuse is blown, return the device to NI for repair.
Caution The power pins, +5 V and GND, connect to the computer power supply and are
not isolated. Do not connect a +5 V power pin directly to GND or connect a +5 V or GND
pin to any other voltage source. Doing so may cause injury or permanently damage the
NI 6528/6529 components. National Instruments is not liable for any damage or injury
resulting from such a connection.
Table 5. NI 6528 Maximum Power Ratings
Power Rating
Maximum DC voltage across the terminals (VOUT)60 VDC
Maximum AC voltage across the terminals (VOUT)30 Vrms (42 Vpk)
Maximum current (IF)150 mA*
*With all relays carrying 150 mA and all inputs driven to 60 V, the total power dissipation can approach 20 W. The maximum
switching capacity CompactPCI systems must be derated according to the ambient temperature and cooling capacity of your
system to prevent the device from overheating. The PXI chassis has built-in fans to handle 25 W per slot.