SN74ALS990 Datasheet | Texas Instruments

description This 8-bit latch is designed specifically for storing the contents of the input data bus and providing the capability of reading back the stored data onto the input data bus. DW OR N PACKAGE (TOP VIEW) OERB 1 1D 2 2D 3 3D 4 4D 5 5D 6 6D 7 7D 8 8D 9 GND 10 20 VCC 19 1Q 18 2Q 17 3Q 16 4Q 15 5Q 14 6Q 13 7Q 12 8Q 11 LE The eight latches are transparent D-type latches. While the latch-enable (LE) input is high, the Q outputs follow the data (D) inputs. Read back is provided through the output-enable (OERB) input. When OERB is taken low, the data present at the output of the data latches is allowed to pass back onto the input data bus. When OERB is taken high, the output of the data latches is isolated from the D inputs. OERB does not affect the internal operation of the latches; however, precautions should be taken not to create a bus conflict. The SN74ALS990 is characterized for operation from 0°C to 70°C. logic symbol† OERB EN2 C1 1D 1D 3 2D 4 3D 5 4D 6 5D 7 6D 8 7D 9 8D 19 1Q 18 2Q 17 3Q 16 4Q 15 5Q 14 6Q 13 7Q 12 8Q † This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. - POST OFFICE BOX 655303 DALLAS, TEXAS 75265 Copyright © 1995, Texas Instruments Incorporated 1 SN74ALS990 8-BIT D-TYPE TRANSPARENT READ-BACK LATCH SDAS027B - APRIL...