DRAM pin-count reduction technique: To reduce the number of pins on high-capacity DRAM chips, what address technique is used so a single set of pins can carry both row and column addresses at different times?

Difficulty: Easy

Correct Answer: multiplexing

Explanation:


Introduction / Context:
Dynamic RAM devices require many address lines, but package pin counts must be constrained for cost and size. The industry solution is to time-multiplex the address bus, sending row and column addresses sequentially over the same pins.


Given Data / Assumptions:

  • High-capacity DRAM with large address space.
  • Desire to limit package pin count.
  • Standard DRAM control pins: RAS (row address strobe) and CAS (column address strobe).


Concept / Approach:
Address multiplexing uses the same physical address pins twice per access: first the controller presents the row address and asserts RAS; then it presents the column address and asserts CAS. Internally, DRAM latches each portion separately, allowing many address bits with fewer external pins.


Step-by-Step Solution:

Place row address on the address pins and assert RAS.Place column address on the same pins and assert CAS.DRAM uses both to select the target cell(s).Result: fewer external pins without sacrificing address space.


Verification / Alternative check:
Pinouts and timing diagrams for common DRAMs show A0..An used with RAS/CAS to latch row and column portions of the address.


Why Other Options Are Wrong:

  • conversion/programming/firmware: These terms do not describe hardware pin reuse for addressing.


Common Pitfalls:
Confusing multiplexing with bank interleaving or burst modes; overlooking the role of RAS/CAS strobes in timing.


Final Answer:
multiplexing

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion