Texas Instruments SN74ACT1284

the act1284 devices are designed for asynchronous two-way communication between data buses. the control function minimizes external timing requirements. the devices allow data transmission in either the a-to-b or the b-to-a direction for bits 1 2 3 and 4 depending on the logic level at the direction-control (dir) input. bits 5 6 and 7 however always transmit in the a-to-b direction. the output drive for each mode is determined by the high-drive (hd) control pin. when hd is high the high drive is delivered by the totem-pole configuration and when hd is low the outputs are open drain. this meets the drive requirements as specified in the ieee 1284-i (level-1 type) and the ieee 1284-ii (level-2 type) parallel peripheral-interface specification.