BCD-to-7-Segment Driver 7447 — Determine Outputs for Digit 9 Given a 7447 common-anode driver with inputs RBI = 0, LT = 1, and BCD A3 A2 A1 A0 = 1 0 0 1 (decimal 9), list the states of RBO and segments a–g (active-LOW outputs).

Introduction / Context:
The 7447 is a BCD-to-7-segment decoder/driver intended for common-anode displays. Its outputs are active-LOW, meaning a segment is lit when its output pin drives LOW. Understanding the mapping from BCD inputs to segment patterns, and the function of RBI/RBO and LT pins, is essential for display interfacing and ripple-blanking cascades.

Given Data / Assumptions:

• Inputs: A3 A2 A1 A0 = 1 0 0 1 (decimal 9).
• RBI (Ripple Blanking Input) = 0; LT (Lamp Test) = 1 (inactive).
• Outputs are active-LOW: output 0 lights the segment; 1 turns it off.

Concept / Approach:
For the digit 9, the illuminated segments on a standard 7-segment display are a, b, c, d, f, g, while segment e is off. Since outputs are active-LOW, those lit segments must be 0, and the unlit segment e must be 1. RBO (Ripple Blanking Output) propagates blanking when displaying leading zeros; for any nonzero digit with RBI = 0, RBO = 1 (no blanking signal forwarded).

Step-by-Step Solution:
Map the pattern for 9: segments {a, b, c, d, f, g} ON; segment {e} OFF.Translate to active-LOW levels: a=0, b=0, c=0, d=0, f=0, g=0, e=1.Determine RBO: input is 9 (nonzero), so RBO = 1.Assemble full listing: RBO=1; a=0 b=0 c=0 d=0 e=1 f=0 g=0.

Verification / Alternative check:
Datasheet truth tables for the 7447 confirm the segment coding for decimal 9 and the ripple blanking operation: RBO drives LOW only when the device blanks a zero with RBI asserted; otherwise RBO remains HIGH.

Why Other Options Are Wrong:

• Any option with d = 1: would turn segment d off, contradicting the standard 9 pattern.
• Any option with RBO = 0: indicates leading-zero blanking; not applicable for a nonzero digit.

Common Pitfalls:
Forgetting that 7447 outputs are active-LOW (0 = ON), and confusing RBI/RBO behavior for the zero digit only.

Final Answer:
RBO = 1, a = 0, b = 0, c = 0, d = 0, e = 1, f = 0, g = 0