DM74LS491 Datasheet | National Semiconductor

Description The ten-bit counter can count up count down set and load 2 LSB’s 2 MSB’s and 6 middle bits high or low as a group All operations are synchronous with the clock SET overrides LOAD COUNT and HOLD LOAD overrides COUNT COUNT is conditional on CIN otherwise it holds All outputs are enabled when OE is low otherwise HIGH-Z The 24 m A IOL outputs are suitable for driving RAM PROM address lines in video graphics systems Features Benefits Y Y Y Y Y CRT vertical and horizontal timing generation Bus-structured pinout 24-pin SKINNYDIP saves space TRI-STATE outputs drive bus lines Low current PNP inputs reduce loading Connection Diagram Top View Standard Test Load TL L 8332 - 2 TL L 8332 - 1 Order Number DM54LS491J DM74LS491J or DM74LS491N See NS Package Number J24F or N24C Function Table OE CK SET LD CNT CIN UP D9-D0 H L L L L L L X Q9-Q0 Operation X H L L L L L X X L H H H H X X X H L L L X X X X H L L X X X X X L H X X D X X X X Z Hi-Z H Set all HIGH D LOAD D Q HOLD Q HOLD Q plus 1 Count UP Q minus 1 Count DN u u u u u u TRI-STATE is a registered trademark of National Semiconductor Corp C1995 National Semiconductor Corporation TL L 8332 RRD-B30M115 Printed in U S A Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage VCC Input Voltage 7V 5 5V Off-State Output Voltage Storage Temperature 5 5V b 65 to a 150 C Operating Conditions Symbol VCC TA tw t SU th Supply Voltage Operating Free-Air Temperature Width of Clock Set-Up Time Hold Time Case temperature Parameter Min 45 b 55 Military Typ 5 Max 55 125 Min 4 75 0 40 35 50 b 15 mercial Typ 5 Max 5 25 75 Units V C ns High Low 40 35 60 0 ns b 15 Electrical Characteristics Over Operating Conditions Symbol VIL VIH VIC IIL IIH II VOL Parameter Low-Level Input Voltage High-Level Input Voltage Input Clamp Voltage Low-Level Input Current High-Level Input Current...