Important Digital Logic and Design Short Questions
Chapter: 40
Question 1:
What is the main difference between Static RAM (SRAM) and Dynamic RAM (DRAM) in terms of memory cell construction?
Answer:
SRAM uses multiple transistors to create a latch for storing data, while DRAM uses a single transistor and capacitor, making DRAM cells more compact but requiring periodic refreshing to maintain data.
Chapter: 40
Question 2:
Why does Dynamic RAM (DRAM) require a refresh cycle?
Answer:
DRAM cells use capacitors that can lose charge over time, so a refresh cycle is needed to periodically recharge these capacitors to prevent data loss.
Chapter: 40
Question 3:
How does address multiplexing reduce the number of address lines in DRAM?
Answer:
Address multiplexing splits the address into row and column parts, using the same address lines for both but at different times, thus halving the number of address lines needed.
Chapter: 40
Question 4:
What are the roles of the RAS and CAS signals in DRAM address multiplexing?
Answer:
RAS (Row Address Strobe) latches the row address, while CAS (Column Address Strobe) latches the column address, enabling the DRAM to select the correct memory cell for reading or writing.
Chapter: 40
Question 5:
How does the Refresh Control and Timing circuit function in a DRAM system?
Answer:
It generates refresh cycles and configures the Data Selector to refresh all memory cells in a selected row, ensuring data integrity by periodically recharging the capacitors in DRAM cells.
Chapter: 41
Question 6:
What is the purpose of the RAS signal in a DRAM read cycle?
Answer:
The RAS (Row Address Strobe) signal latches the row address in a DRAM read cycle, enabling data access from the specified row.
Chapter: 41
Question 7:
How does the CAS signal affect data reading in FAST Page Mode?
Answer:
In FAST Page Mode, the CAS (Column Address Strobe) signal toggles to select successive columns, allowing faster read access from consecutive columns in the same row.
Chapter: 41
Question 8:
What distinguishes Burst Refresh Mode from Distributed Refresh Mode?
Answer:
Burst Refresh Mode refreshes all rows consecutively in one cycle, while Distributed Refresh Mode intersperses refresh cycles between normal operations.
Chapter: 41
Question 9:
Describe the difference between RAS only refresh and CAS before RAS refresh.
Answer:
RAS only refresh latches the row address with RAS going low and keeps CAS inactive, while CAS before RAS refresh activates CAS before RAS to use an internal refresh counter.
Chapter: 41
Question 10:
What is a key feature of Fast Page Mode DRAM?
Answer:
Fast Page Mode DRAM allows faster access by reading or writing successive columns in the same row more quickly than random access DRAM.