DALLAS (February 6, 1995) -- The industry's first dedicated IEEE1284 parallel port interface device from Texas Instruments allows designers of personal computers and workstations to improve the reliability of high-speed data transfers to peripherals such as printers, plotters and optical scanners.
The IEEE1284 standard serves as a replacement to the "Centronics" parallel port interface traditionally seen on most PC to peripheral interfaces. Printer manufacturers who have implemented IEEE1284 have done so with application specific integrated circuits (ASICs), which can generate significant system noise.
"Almost all printer manufacturers have committed to using IEEE1284 in their next generation products," said Gary Reichmuth, strategic marketing specialist at TI. "This device eliminates some of the problems inherent in ASIC solutions, including high levels of noise in the communication channel, and the time and expense involved with ASIC development."
Designated SN74ACT1284, the new 7-bit TI device has three-state outputs which drive the IEEE1284 communication channel directly. To reduce the chance of faulty signals being transferred over the system's parallel port, the ACT1284 features a finely-tuned output edge-rate control (OECTM) circuit and an enhanced input hysterisis circuit.
The OEC circuit effectively controls noise and signal reflections over long transmission lines, such as ribbon cables. And with a high input hysterisis of 400 milli-volts, the ACT1284 is better able to distinguish between transient interference and actual data signals, reducing the chance that electrical interference will be interpreted as a data signal.
The ACT1284 allows the printer or other peripheral to be connected to the host PC while the system is active. This live insertion capability is needed to support the plug-and-play initiative supported by next generation operating systems, such as Microsoft Windows™ 95. Plug-and-play allows a PC user to simply plug a peripheral into the parallel port, and the operating system automatically reconfigures itself by selecting the drivers needed for the specific peripheral and initializing the device. No manual intervention is required. Microsoft is a supporter of the IEEE1284 standard.
The ACT1284 provides a reliable transfer of data over cables of up to 30 feet in length and at speeds up to two megabytes per second. The ACT1284 device can be configured for operation on either the computer host or the peripheral end of the cable. Since some systems must remain backward compatible with the older Centronics standard interface, the ACT1284's outputs can be switched from its normal totem-pole output to an open-drain output.
The SN74ACT1284 comes in standard 20-pin SOIC or SSOP packages. The device is available now from Texas Instruments and its authorized distributors. Suggested resale pricing in quantities of 1,000 is $0.80.
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An industry pioneer and the world leader in digital signal processors for more than 10 years, Texas Instruments Semiconductor Group provides innovative solutions to more than 15,000 customers worldwide in the computer, communications, consumer, automotive, military and industrial markets. TI offers a unique breadth of digital and mixed-signal products and technologies, hardware and software development tools, design information services and global support.
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