48-Bit Isolated Digital I/O 48-Bit Isolated Digital I/O NI 6527 • 24 optically isolated digital inputs (0-28 VDC) • 24 isolated, solid-state relay digital outputs (0-60 VDC, 0-30 Vrms) • Switch up to 120 mA • Digital filtering on inputs • Messaging (change notification) • NI-DAQ driver simplifies configuration and measurements Operating Systems • Windows 2000/NT/XP • Real-time performance with LabVIEW (page 134) • Others such as Linux and Mac OS X (page 187) Recommended Software Models • LabVIEW • LabWindows/CVI • Measurement Studio • NI PCI-6527 • NI PXI-6527 Other Compatible Software • Visual Basic • C/C++, C# Driver Software (included) • NI-DAQ 7 Family NI 6527 Bus PCI, PXI Digital I/O Lines 24 inputs and 24 outputs Maximum Rate Software timed Isolation 60 VDC channel to channel Handshaking I/O – 8255 chipset – Change Notification ✓ Pattern Matching – Table 1. Digital I/O Products Specifications Summary (See page 385 for detailed specifications.) Overview and Applications Debouncing Filter for Glitch Removal NI 6527 devices are 48-bit, parallel, isolated DIO interfaces for PCI and PXI. They have 24 optically isolated digital inputs and 24 solidstate relay outputs. NI 6527 devices can sense digital levels up to 28 VDC and switch currents up to 120 mA. The channel-to-channel isolated inputs and outputs protect your system, reduce noise, and break ground loops. Each input line can be digitally filtered to prevent a momentary glitch or spike from affecting the line state. When you use messaging, filtering blocks spurious change events caused by noise on the input line. Features Digital Inputs You can use the 24 optically isolated inputs of the NI 6527 devices to read the status of external logic at TTL and non-TTL levels. Each input channel has two differential isolated terminals – one for the signal and one for its reference. A potential difference of 2 to 28 VDC between the two terminals registers as a logic high. Logic low is between 0 and 1 V. The inputs feature 60 VDC isolation from the computer and between channels. Messaging – Change Notification NI 6527 devices can generate a message when one or more userselected input lines changes, either from low to high, high to low, or both. Once notified of a change, NI-DAQ can read the status of other input lines, set outputs, or perform some other programmed operation. Using this feature, you can monitor lines without polling, thus using your CPU more efficiently. Data Acquisition and Signal Conditioning Logic Level O to 28 VDC input and 0 to 60 VDC (30 Vrms) output Digital Switch Outputs and Power-Up States The 24 solid-state relay outputs on the NI 6527 devices can switch external devices, including those requiring high input currents, and control digital logic levels at both TTL and non-TTL levels. Each relay output has two terminals. Writing a logic low to an output closes the connection between the terminals; writing a logic high opens the connection. Depending on how your load connects to the terminals, an output can either source or sink currents. By adding pull-up resistors externally and, if needed, an isolated power supply, you can output digital signals that source or sink currents. The solidstate relay outputs have a maximum switching capacity of 60 VDC, 30 Vrms, or 120 mA, and are isolated up to 60 VDC or 30 Vrms from the computer and between channels. NI 6527 device outputs include circuitry to protect against transient currents above the rated values. When excessive current flows through the relay, the relay limits the current to approximately 260 mA (typical). National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com 377 I/O Connector The I/O connector for an NI 6527 is a 100-pin female connector, and the pinout is shown in Figure 1. For a shielded cable/accessory combination, use the SH100-100-F cable with the SCB-100 accessory. NI 6527 devices are also compatible with the CB-100 kit, which includes two 50-pin connector blocks and ribbon cable. For 5 V nonisolated applications, the +5 V and GND lines from the computer, available on the I/O connector, eliminate the need for an external power supply. Port 0 Isolation PCI MITE Interface Port 1 Isolation Digital I/O Circuitry (FPGA) Port 2 Isolation EEPROM Port 3 Isolation Port 4 Isolation Port 5 Isolation Data Acquisition and Signal Conditioning Driver Software With NI-DAQ driver software, you can interactively configure your devices, write custom programs, and easily perform digital I/O. You can also use change notification and messaging so that when a line state change is detected, the software can perform another programmed operation. Change notification eliminates polling, decreases the load on the CPU and bus, and improves the efficiency of the system. NI-DAQ also provides numerous example programs for LabVIEW and other development environments to quickly get you started with your application. DIG+2.7 DIG–2.7 DIG+2.6 DIG–2.6 DIG+2.5 DIG–2.5 DIG+2.4 DIG–2.4 DIG+2.3 DIG–2.3 DIG+2.2 DIG–2.2 DIG+2.1 DIG–2.1 DIG+2.0 DIG–2.0 DIG+1.7 DIG–1.7 DIG+1.6 DIG–1.6 DIG+1.5 DIG–1.5 DIG+1.4 DIG–1.4 DIG+1.3 DIG–1.3 DIG+1.2 DIG–1.2 DIG+1.1 DIG–1.1 DIG+1.0 DIG–1.0 DIG+0.7 DIG–0.7 DIG+0.6 DIG–0.6 DIG+0.5 DIG–0.5 DIG+0.4 DIG–0.4 DIG+0.3 DIG–0.3 DIG+0.2 DIG–0.2 DIG+0.1 DIG–0.1 DIG+0.0 DIG–0.0 +5 V GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 DIG+5.7 DIG–5.7 DIG+5.6 DIG–5.6 DIG+5.5 DIG–5.5 DIG+5.4 DIG–5.4 DIG+5.3 DIG–5.3 DIG+5.2 DIG–5.2 DIG+5.1 DIG–5.1 DIG+5.0 DIG–5.0 DIG+4.7 DIG–4.7 DIG+4.6 DIG–4.6 DIG+4.5 DIG–4.5 DIG+4.4 DIG–4.4 DIG+4.3 DIG–4.3 DIG+4.2 DIG–4.2 DIG+4.1 DIG–4.1 DIG+4.0 DIG–4.0 DIG+3.7 DIG–3.7 DIG+3.6 DIG–3.6 DIG+3.5 DIG–3.5 DIG+3.4 DIG–3.4 DIG+3.3 DIG–3.3 DIG+3.2 DIG–3.2 DIG+3.1 DIG–3.1 DIG+3.0 DIG–3.0 +5 V GND 16 Port 1 16 Port 2 16 Port 3 16 Port 4 16 Port 5 16 Figure 2. NI 6527 Block Diagram Related Products SCXI Signal Conditioning . . . . . . . . . . . . . . . . . . . . . . .See page 270 Digital Signal Conditioning Accessories . . . . . . . . . . . .See page 349 Ordering Information NI PCI-6527 ..................................................................777810-01 NI PXI-6527 ..................................................................777802-01 Includes NI-DAQ driver software For information on extended warranty and value added services, see page 20. Recommended Configurations DAQ Device PCI-6527 PXI-6527 Accessory CB-100 kit (777812-01) SCB-100 (776990-01) Cable Kit includes R1005050 ribbon cable SH100-100-F (185095-02) See page 382 for accessory and cable information. BUY ONLINE! Visit ni.com/info and enter pci6527 and/or pxi6527. Figure 1. NI 6527 I/O Connector 378 Port 0 I/O Connector By default, the solid-state relays power up open (digital lines high). You can configure the power-up state of each output line independently with a software utility located in the Developer Zone. For more information, go to ni.com/info and enter ex95u3. PCI or PXI/CompactPCI Bus 48-Bit Isolated Digital I/O 48-Bit Isolated Digital I/O National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com Digital I/O Connectivity and Signal Conditioning Digital I/O Connectivity and Signal Conditioning Cables, Connector Blocks, and Signal Conditioning Choose your Digital I/O cables, connector blocks, and signal conditioning in two easy steps. Step 1. Choose your connector block and cable. (see digital I/O accessories section for details) Device PCI-6527, PXI-6527 Connector Block CB-100 Kit SCB-100 CA-1000, CB-50, CB-50LP PCI-6503, PC-DIO-24 DAQCard-DIO-24 PCI-DIO-96, PXI-6508 CA-1000, CB-50, CB-50LP CA-1000, CB-50, CB-50LP CB-100 Kit SCB-100 CA-1000, CB-50, CB-50LP PC-DIO-96 CB-100 Kit SCB-100 CA-1000, CB-50, CB-50LP Cables Kit includes R1005050 cable SH100-100-F R1005050 (splits into two 50-pin connectors); with this cable, you can use two accessories from this group with one NI 6527 device SH50-50 or NB1 PSH27-50F-D Kit includes R1005050 cable SH100-100-F NB5 (Splits into two 50-pin connectors); with this cable, you can use two accessories from this group with each device. Kit includes NB5 cable SH100-100-F NB5 (Splits into two 50-pin connectors); with this cable, you can use two accessories from this group with each device. Step 2 (Optional). Choose your signal conditioning hardware and enclosures. SCXI Signal Conditioning System (Page 270 ) – – ✓ ✓ ✓ ✓ ✓ ✓ SSR Series Modules (Page 349 ) – – ✓ ✓ ✓ ✓ ✓ ✓ SC-206x Device (Page 349) – – ✓ ✓ ✓ ✓ ✓ ✓ ER-8, ER-16 Electromechanical Relays (Page 349 ) – – ✓ ✓ ✓ ✓ ✓ ✓ CA-1000 Custom Connectivity Enclosure (Page 351) ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com Data Acquisition and Signal Conditioning Device PCI-6527 PXI-6527 PCI-DIO-96 PXI-6508 PC-DIO-96 PCI-6503 PC-DIO-24 DAQCard-DIO-24 381 Digital I/O Accessories and Cables Digital I/O Accessories and Cables Accessories for Digital I/O SCXI – High-Performance Modular Signal Conditioning (See Figure 1) Figure 1. SCXI High-Performance Signal Conditioning SCXI is a modular high-performance signal conditioning system that serves as a front end to your DIO device. The SCXI modules for DIO offer isolation, extended voltage ranges (up to 250 Vrms), increased current switching capabilities, and expanded channel counts (up to 3,072 I/O lines). In addition to SCXI modules for DIO, your SCXI signal conditioning system can include modules for analog output and generalpurpose switching when cabled to a DIO device. With SCXI, you can create integrated, flexible high-channel-count measurement systems with signal conditioning components tailored to your needs. See page 270 for details on SCXI signal conditioning. SCC – Portable Modular Signal Conditioning National Instruments offers SCC modules for portable low-channel-count digital signal conditioning. These modules mount in a compact, versatile carrier. See page 251 for details on SCC signal conditioning. Digital Signal Conditioning Assessories (See Figure 2) Data Acquisition and Signal Conditioning Figure 2. Digital Signal Conditioning Accessories National Instruments also offers several options for low-channel-count digital signal conditioning. These accessories provide a cost-effective solution for digital I/O systems requiring isolated I/O or relays for controlling external devices. Most of these products cable directly to your National Instruments digital I/O device. See page 349 for details on digital signal conditioning accessories. CA-1000 (See Figure 3) Figure 3. CA-1000 Configurable Signal Connectivity Solution Configurable signal connectivity solution for connecting DIO devices to different types of standard I/O connectors and for incorporating switches and LED indicators. You can place this connector box under a laptop PC, on a benchtop, or in a 19 in. rack. CA-1000 ........................................................................................................See page 351 Dimensions – 30.7 by 25.4 by 4.3 cm (12.1 by 10 by 1.7 in.) SCB-100 (See Figure 4) Figure 4. SCB-100 Shielded Connector Blocks Shielded I/O connector block for easy connection of I/O signals to 100-pin digital I/O devices. The screw terminals are housed in a metal enclosure for protection from noise corruption. Combined with shielded cables, the SCB-100 provides rugged, very low noise signal termination. It also includes general breadboard areas – three on the SCB-100. SCB-100............................................................................................................776990-01 Dimensions – 19.5 by 15.2 by 4.5 cm (7.7 by 6.0 by 1.8 in) CB-50 I/O Connector Block with DIN-Rail Mounting (See Figure 5) Termination accessory with 50 screw terminals for easy connection of field I/O signals to NI 650x and NI 6527 devices. Includes one 50-pin header for direct connection to 50-pin cables. The CB-50 includes a protective plastic base and hardware for mounting the accessory on either a standard DIN rail or flush on a wall or panel. CB-50................................................................................................................776164-90 Dimensions – 13.5 by 7.3 cm (5.3 by 2.9 in.) Figure 5. CB-50 I/O Connector Block 382 National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com Digital I/O Accessories and Cables Termination board with 50 screw terminals for easy connection of field I/O signals to NI 650x and NI 6527 devices. Includes one 50-pin header for direct connection to 50-pin cables. The CB-50LP includes metal standoffs for use on a desktop or for mounting on a custom panel. CB-50LP............................................................................................................777101-01 Dimensions – 13.26 by 7.19 cm (5.22 by 2.83 in.) CB-100 I/O Connector Kit (See Figure 7) Figure 6. CB-50LP I/O Connector Block The first CB-100 kit includes two CB-50 I/O connector blocks and an R1005050 ribbon cable for connecting to a PCI-6527, PXI-6527, PCI-DIO-96, PXI-6508 device. The second CB-100 kit includes two CB-50 I/O connector blocks and/or an NB5 ribbon cable for direct connection to a PC-DIO-96 device. Each CB-50 block includes hardware for mounting the accessory on a standard DIN-rail or panel. CB-100 with 1 m R1005050 cable ..................................................................777812-01 CB-100 with 1 m NB5 cable............................................................................776455-02 Digital I/O Accessories and Cables CB-50LP I/O Connector Block (See Figure 6) RTSI Bus Cables Figure 7. B-100 I/O Connector Kit SH50-50 (See Figure 8) Shielded 50-conductor cable that connects to a PCI-6503 or PC-DIO-24 device and terminates with a 50-pin connector. The kit includes the shielded cable and a 3 in. ribbon cable for connection flexibility. 1 m ....................................................................................................................777720-01 2 m ....................................................................................................................777720-02 Figure 8. H50-50 Shielded Cable Data Acquisition and Signal Conditioning Use RTSI bus cables to connect timing and synchronization signals among measurement, vision, motion, and CAN boards for PCI and ISA. For systems using both long and short boards, order the extended RTSI cable. 2 boards ............................................................................................................776249-02 3 boards ............................................................................................................776249-03 4 boards ............................................................................................................776249-04 5 boards ............................................................................................................776249-05 Extended, 5 boards ..........................................................................................777562-05 SH100-100-F (See Figure 9) Shielded 100-conductor cable that connects to a PCI-6527, PXI-6527, PCI-DIO-96, PXI-6508, or DAQPad-6508 and terminates with a 100-pin 0.050 series D-type connector that attaches directly to 100-pin accessories. 2 m ....................................................................................................................185095-02 Figure 9. SH100-100-F Shielded Cable PSH27-50F-D1 for DAQCard-DIO-24 Shielded cable that connects to the DAQCard-DIO-24 and is terminated with a 50-pin female connector that attaches directly to 50-pin accessories. 0.5 m ..............................................................................................................776989-0R5 1 m ....................................................................................................................776989-01 National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com 383 Digital I/O Accessories and Cables Digital I/O Accessories and Cables Ribbon Cables R1005050 (See Figure 10) Ribbon cable that connects to a PCI-6527, PXI-6527, PCI-DIO-96, PXI-6508 and is terminated with two 50-pin IDC connectors. 1 m ..................................................................................................................182762-01 2 m ..................................................................................................................182762-02 NB1 Cable (See Figure 11) Figure 10. R1005050 Ribbon Cable 50-conductor ribbon cable that connects any device with a 50-pin connector to 50-pin connector accessories. 1 m ..................................................................................................................180524-10 2 m ..................................................................................................................180524-20 NB5 Cable (See Figure 12) 100-conductor ribbon cable that connects to a PC-DIO-96 device (100-pin connector) and is terminated with two 50-pin connectors. 1 m ..................................................................................................................181304-10 2 m ..................................................................................................................181304-20 Figure 11. NB1 Cable Data Acquisition and Signal Conditioning PCB Mounting Connectors for Custom Accessories (See Figure 13) PCB connectors for use in building custom accessories that connect to 100-conductor shielded and ribbon cables. Two types of connectors are available, one for right-angle and one for vertical mounting onto a PCB. 100-pin, female, right-angle mounting ........................................................777778-01 100-pin, female, vertical mounting................................................................777779-01 PCMCIA Strain-Relief Accessory (See Figure 14) Figure 12. NB5 Cable Accessory that attaches to the bottom of your notebook computer and provides adjustable strain relief for one or two PCMCIA cables attached to the installed PCMCIA card(s). PCMCIA strain-relief accessory ....................................................................777550-01 Figure 13. PCB Mounting Connectors Figure 14. PCMCIA Strain-Relief Accessory 384 National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com Digital I/O Overview Digital I/O Overview Digital input/output (DIO) devices are used in a wide variety of applications from automotive design, industrial factory automation, and machine control, to aerospace, laboratory research, and biomedical applications. You can connect NI digital I/O devices to limit and proximity switches, photoelectric sensors, level gauges, pressure switches, gas detectors, pumps, motors, solid-state relays, electromechanical relays, digital data buses, and more. NI DIO devices can be installed in traditional desktop computers using the PCI or ISA bus, connected via USB port, or installed in laptop computers with PCMCIA slots. For the utmost in reliability and mechanical ruggedness, NI also offers PXI digital I/O devices suitable for operation in the LabVIEW Real-Time environment. ER-8 and ER-16 accessories and eight channel SC-2062 enclosure are available. Refer to Table 3 for signal conditioning accessory catalog page numbers. Application Perform basic digital I/O Data Acquisition and Signal Conditioning 1Handshaking ✓ – ✓1 ✓ ✓ ✓ Q: I would like to perform high-speed buffered digital I/O controlled by an external or internal digital clock or handshaking signal. Which digital I/O device do you recommend? A: For high-speed buffered pattern I/O or handshaking I/O, see the hardware-timed NI 653x devices on page 432. Accessory SCXI SSR Series SC-206x ER-8/16 CA-1000 SCB-100 CB-50 CB-50LP CB-100 kit Description Signal conditioning system Digital signal conditioning modules Digital signal conditioning modules Electromechanical relays Configurable connector accessory Shielded connector block I/O connector block I/O connector block I/O connector block kit; includes cable Page 270 321 349 349 351 382 382 383 383 For complete and up-to-date information about accessories, visit ni.com/catalog Table 3. Digital I/O Signal Conditioning Accessories. Digital I/O Lines 24 inputs and 24 outputs Logic Level 28 V input and 60 V output Isolation ✓ Handshaking I/O1 – Change Notification ✓ 96 5 V TTL/CMOS – ✓ – 24 5 V TTL/CMOS – ✓ – supplied by the 8255; only one handshaking mode is available. See page 376 for details. Table 1. Digital I/O Products Specifications Summary (See page 385 for detailed specifications.) 374 – Tech Tip For even higher isolation levels, NI 650x devices can be connected to SCXI-116x signal conditioning modules to provide 450 Vrms of bankto-bank isolation. For lower channel counts, the SC-206x accessories provide eight optically isolated inputs or outputs with 400 Vrms of channel-to-channel isolation. Another option is SSR modules, which provide 4000 Vrms of channel-to-channel isolation in 8, 16, 24, or 32-channel backplanes. For electromechanical relay outputs, the NI 6503 – Table 2. Digital I/O Applications. Signal Conditioning NI 6507 NI 6508 ✓ supplied by the 8255; only one handshaking mode is available. See individual product details on the following pages for more information. See page 376 for details. Isolation physically and electrically separates two parts of a circuit and provides several advantages. It breaks ground loops, improves common-mode voltage and noise rejection, and it permits two parts of the circuit to be at different voltage levels. Isolation protects both computer circuitry and human operators. Industrial applications often require isolation to protect the electronics from transient voltage spikes and to provide greater common-mode noise rejection in electrically noisy environments containing machinery and inductive loads. In the case of channel-to-channel isolated I/O, each channel has its own ground terminal. In bank-to-bank isolated devices, each bank (or group) consists of several channels that share the same ground but are isolated from other banks. NI 6527 devices provide 60 VDC of built-in channel-to-channel isolation between each I/O channel. Bus PCI PXI PCI PXI ISA USB PCI PCMCIA ISA Product Families NI 6527 NI 650x Isolated Low-Cost DIO (p. 377) DIO (p. 379) ✓ ✓ 1Handshaking Isolation Product PCI-6527 PXI-6527 PCI-DIO-96 PXI-6508 PC-DIO-96 DAQPad-6507/6508 PCI-6503 DAQCard-DIO-24 PC-DIO-24 Mode of Operation Software timed Hardware timed Handshaking I/O Transfer data with fixed timing between points Transfer data where both the device under test and measurement device can pause the transfer Run a user-defined software Change Notification routine when a user-defined and Pattern Matching DIO event occurs Choose Your Digital I/O Hardware Family NI 6527 NI 653x High-Speed DIO (p.432) ✓ National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com 8255 Chipset – Pattern Matching – Page 377 ✓ ✓ 379 ✓ ✓ 379 Digital I/O Overview Connectivity Software-Timed Digital I/O For shielded screw-terminal connections to your NI 6527 or NI 6508 device, use the SCB-100 connector block and shielded SH100-100-F cable. Unshielded connector blocks and cables are also available, such as the CB-100 kit which includes an unshielded ribbon cable. For custom connectivity, the CA-1000 accessory enclosure can be used for convenient connection to pushbutton/rocker switches, banana jack cables/probes, and LED indicators. Refer to Digital I/O Accessories and Cables on page 382 for more details and options. Software-timed digital I/O, also referred to as unstrobed or static digital I/O, implies that the writing to digital output lines and reading from digital input lines is performed by software command. A single write or read operation is performed with each software command. Depending on the voltage and current requirements, you can use either NI 650x or NI 6527 softwaretimed devices to monitor and control switches, relays, actuators, annunciators, fans, lights, and motors. The maximum speed for software-timed digital I/O operations depends on the computer processor speed, communication bus, and operating system. For highest performance and greatest determinism in the timing of your software-timed digital I/O, use a PXI system running LabVIEW Real-Time. Figure 1. Test DIO device hardware and signal connections using Data Acquisition and Signal Conditioning a Measurement & Automation Explorer test panel. For laboratory and test and measurement applications, the most commonly used logic levels are 5 V TTL and TTL-compatible CMOS. In industrial control applications, 24 V levels with isolation are common and digital I/O devices may include electromagnetic relays, motor controls, switches, valves, or pumps. NI offers digital logic levels from nonisolated 5 V TTL/CMOS on NI 650x devices, up to 28 V input and 60 V output on NI 6527 devices. NI 6527 devices also offer channel-to-channel optical isolation and higher current switching capability on the outputs (120 mA). For even higher voltage and isolation levels, the NI SCXI-1162, SCXI-1162HV, and SCXI-1163 modules provide signal conditioning from 5 V TTL/CMOS up to 240 VAC/VDC in optically isolated banks of four lines each. Digital I/O Overview Voltage Levels Tech Tip Q: I am controlling digital lines and relays, and I need to set the power-up states of each line in software. Can I do this? Figure 2. You can use LabVIEW to create powerful DIO applications. This figure represents the graphical user interface of a software timed DIO application on an A: You can do this with the NI 6527 isolated digital I/O devices. You can configure the power-up state of each output line independently with a utility in the Developer Zone. For more information, see page 377 or visit ni.com/info and enter ex95u3. NI 650x device. See page 43 for more information about LabVIEW. National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com 375 Data Acquisition and Signal Conditioning Digital I/O Overview Digital I/O Overview Hardware-Timed Digital I/O Power-Up States Hardware-timed digital I/O, also referred to as high-speed digital I/O, implies that the writing and reading of digital lines is controlled by an external or internally generated clock signal. The clock signal latches the digital data into or out of a buffer, which can be streamed at high speed to the computer. With hardware-timed digital I/O, software commands are similar to buffered data acquisition command and an array of data is passed with each read or write operation. NI 653x devices can be used in either a hardware-timed or a software-timed manner. Some applications require that the digital I/O device power up with a determined value on the data lines. This procedure ensures that equipment connected to the digital I/O device is not damaged during the time after power is applied and before the software application begins running. All NI digital I/O devices power up with a known state on the digital I/O lines, either logic high, logic low, or high impedance. NI 6527 devices offer software programmable power-up states on each line that can be configured using a software utility located in the Developer Zone. For more information on NI 653x devices see page 432. For more information, visit ni.com/info and enter ex95u3. Handshaking Digital I/O Change Notification and Pattern Matching Handshaking digital I/O refers to transfers of digital data between the digital I/O device and a peripheral. Both parties in the transfer control a handshaking line and can pause the operation if they are unable to keep up with the data rate. NI 650x devices offer 8255 Mode 2 bidirectional transfers at typical constant sustainable rates of 1 to 10 kbytes/s using a 233 MHz Pentium computer. To monitor digital lines without continuously polling their state, you can use Change Notification on NI 6527 devices to notify your application when one or more digital input lines changes from low to high, high to low, or both. You can configure NI 650x devices to provide pattern matching when the input lines on a port match a specific pattern. In a PXI LabVIEW Real-Time application, change notification and pattern matching can be used to deterministically trigger execution for high-reliability real-time event response. For more information on high-speed handshaking, see the NI 653x devices on page 432. NI offers a complete array of digital I/O products for connection to any digital data bus or device. 376 National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • [email protected] • ni.com