SN74AS641 Overview
These devices transmit data from the A bus to the B bus or from the B bus to the A bus, depending upon the level at the direction-control (DIR) input. The output-enable (OE) input disables the device so that the buses are effectively isolated. The -1 versions of the SN74ALS641A and SN74ALS642A are identical to the standard versions, except that the remended maximum IOL is increased to 48 mA in the -1 versions.