TI's SN74ACT1284 enables fast, bi-directional communications
Texas Instruments has introduced the industry's first discrete bus driver solution compliant to the IEEE 1284 high-speed, high-integrity parallel port standard for bi-directional peripheral interface.
The device, the SN74ACT1284, is a 7-bit bus interface with 3-state outputs that directly drive the communications channel. It is compatible with all 1284 electrical specifications and supports reliable data transfer over cables up to 30 feet in length at speeds of two Mbytes/s.
TI's SN74ACT1284 enables fast, bi-directional communications
The 1284 standard provides for communication 10 to 50 times faster than conventional parallel port interfaces.
The ACT1284 features an Output Edge-rate control circuit (OEC) that minimizes noise caused by high-speed rise and fall times. In addition, a center pin Vcc and GND reduces package inductance noise. A high input hysteresis of 400 millivolts-an even broader buffer than that required by 1284 -- also reduces the chances that electrical interference will by misinterpreted as data.
The ACT1284 uses four bits for bi-directional data transfer. The three remaining bits are configured for control functions when the device is located on the host and status functions when it is located on the peripheral. For compat-ibility with the older "Centronics" standard interface, the device's outputs can be switched from Totem-pole to Open-drain.
The device also is plug and play compatible to allow the printer or other peripherals to be connected to the host while the system remains active.
The SN74ACT1284 is available today from Texas Instruments and authorized distributors.
SN74ACT1284 20-pin SOIC $0.85
20-pin SSOP $0.85
Suggested resale price in quantities of 1,000.
July - August 1995, vol. 12, no. 5
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