MM74C85 4-Bit Magnitude Comparator
October 1987 Revised May 2002
MM74C85 4-Bit Magnitude Comparator
General Description
The MM74C85 is a four-bit magnitude comparator which will perform comparison of straight binary or BCD codes. The circuit consists of eight comparing inputs (A0, A1, A2, A3, B0, B1, B2, B3), three cascading inputs (A > B, A < B and A = B), and three outputs (A > B, A < B and A = B). This device compares two four-bit words (A and B) and determines whether they are “greater than,” “less than,” or “equal to” each other by a high level on the appropriate output. For words greater than four-bits, units can be cascaded by connecting the outputs (A > B, A < B, and A = B) of the least significant stage to the cascade inputs (A > B, A < B and A = B) of the next-significant stage. In addition the least significant stage must have a high level voltage (VIN(1)) applied to the A = B input and low level voltage (VIN(0)) applied to A > B and A < B inputs.
Features
s Wide supply voltage range: 3.0V to 15V s Guaranteed noise margin: 1.0V s High noise immunity: 0.4 VCC (typ.) s Low power: TTL compatibility: fan out of 2 driving 74L s Expandable to 'N' stages s Applicable to binary or BCD s Low power pinout: 74L85
Ordering Code:
Order Number MM74C85N Package Number N16E Package Description 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Connection Diagram
Top View
© 2002 Fairchild Semiconductor Corporation
DS005886
www.fairchildsemi.com
MM74C85
Truth Table
Comparing Inputs A3, B3 A3 > B3 A3 < B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A2, B2 X X A2 > B2 A2 < B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A1, B1 X X X X A1 > B1 A1 < B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A0, B0 X X X X X X A0 > B0 A0 < B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 X X X X X X X X H L L L H H H L Cascading Inputs A>B AB H L H L H L H L H L L L H H H L Outputs A
