Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
274 views
in Electronics by (115k points)
closed by
An 8 Kbyte ROM with an active low Chip Select input\(\left( {\overline {{\rm{CS}}} } \right)\) is to be used in an 8085 microprocessor-based system. The ROM should occupy the address range 1000H to 2FFFH. The address lines are designated as A15 to A0, where A15 is the most significant address bit. Which one of the following logic expressions will generate the correct \(\overline {{\rm{CS}}}\) signal for this ROM?
1. A15 + A14 + (A 13 . A12 + A̅13 . A̅ 12)
2. A15 . A14 . (A13 + A12)
3. A̅15 . A̅ 14 . (A 13 . A̅12 
4. A̅15 + A̅14 + (A13 . A12)

1 Answer

0 votes
by (152k points)
selected by
 
Best answer
Correct Answer - Option 1 : A15 + A14 + (A 13 . A12 + A̅13 . A̅ 12)

Given address range: 1000 H to 2FFF

∴ Total No. of address lines = 13 i.e.  \(\begin{array}{*{20}{c}} {2{\rm{FFF}}}\\ {\underline {1000} }\\ {1{\rm{FFF}}} \end{array}\)

(1FFF)H = (0001 1111 1111 1111)2 = 13 address lines

i.e. \(\begin{array}{*{20}{c}} {{{\rm{A}}_{15}}}&{{{\rm{A}}_{14}}}&{{{\rm{A}}_{13}}}&{{{\rm{A}}_{12}}}&{{{\rm{A}}_{11}}}&{{{\rm{A}}_{10}}}& \cdots &{{{\rm{A}}_2}}&{{{\rm{A}}_1}}&{{{\rm{A}}_0}}&{}\\ 0&0&0&1&0&0&{}&0&0&0&{ = {{\left( {1000} \right)}_{\rm{H}}}}\\ {}&{}& \vdots &{}&{}& \vdots &{}&{}&{}&{}&{}\\ 0&0&1&0&1&1&{}&1&1&1&{ = {{\left( {2{\rm{FFF}}} \right)}_{\rm{H}}}} \end{array}\)

i.e. \(\begin{array}{*{20}{c}} {{{\rm{A}}_{15}}}&{{{\rm{A}}_{14}}}&{{{\rm{A}}_{13}}}&{{{\rm{A}}_{12}}}\\ 0&0&0&1\\ 0&0&1&0 \end{array}\)

To provide \(\overline {{\rm{CS}}}\) as low, the condition is

A15 = A14 = 0 and A13 = A12 = (01) or (10)

i.e. A15 = A14 = 0 and A13 , A12 shouldn't be (11) , (00)

Thus it is A15 + A14 + (A 13 . A12 + A̅13 . A̅ 12)

Hence option (1) is correct

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...