Questions and Answers
What is the advantage of DRAM memory?
What is the disadvantage of DRAM memory?
How many address lines are used in Direct I/O method to identify an I/O device?
What is the difference between I/O Read and I/O Write control signals?
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How does the MPU communicate with an I/O device in Memory-Mapped I/O method?
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What is the type of memory that stores data in the form of charge in capacitors?
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Which of the following statements is true about Direct I/O method?
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What is the main difference between Direct I/O and Memory-Mapped I/O methods?
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How many input devices and output devices can be identified by the MPU in Direct I/O method?
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What is the main disadvantage of using DRAM memory?
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Study Notes
Memory Types
- ROM (Read Only Memory): data can only be read, no writing is allowed; used to store permanent programs; nonvolatile type of memory
- EPROM (Erasable Programmable Read Only Memory): programmable by user, information can be erased by exposing to ultraviolet light, and reprogrammed using EPROM programmer; disadvantage: all data gets erased even if only one bit needs to be changed
- EEPROM (Electrically Erasable Programmable Read Only Memory): similar to EPROM, but erasing is done by electrical signals; advantage: memory location can be selectively erased and reprogrammed; disadvantage: manufacturing process is complex and expensive
- R/W Memory (Read/Write Memory): also called RAM, allows reading and writing data, volatile type of memory; used to check execution of programs
R/W Memory Subtypes
- SRAM (Static RAM): consists of flip-flops, bit status remains until next write operation or power supply is switched off; advantages: fast access time, no refreshing required; disadvantages: low package density, expensive
- DRAM (Dynamic RAM): stores data in capacitors, requires refreshing to maintain charge, high package density, low cost; disadvantage: requires refreshing circuit every few milliseconds
Microprocessor Clock
- Also called clock rate, measures speed at which microprocessor executes instructions
- Measured in megahertz (MHz) or gigahertz (GHz)
- CPU requires a fixed number of clock ticks to execute each instruction
- Faster clock speed means more instructions can be executed per second
Classification of Memory
- ROM (Read Only Memory): data can only be read, no writing allowed; used to store permanent programs; nonvolatile
- Masked ROM: program or data permanently installed at time of manufacturing; cannot be altered; expensive but economic for large quantities
- PROM (Programmable Read Only Memory): similar to masked ROM, but has fuse links; can be programmed, but disadvantage: no chance of re-growing fuse, and programmed data can be altered due to aging
I/O Devices and Interfacing
- MPU communicates with outside world through I/O devices
- Two methods of I/O device identification and communication: Direct I/O (Peripheral) and Memory-Mapped I/O
- Direct I/O uses two instructions (IN & OUT) for data transfer, MPU uses 8 address lines to send I/O device address, and can differentiate between input and output devices using control signals IOR and IOW
- Memory-Mapped I/O uses 16 address lines to identify I/O device, similar to communicating with memory location
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Description
This quiz covers the basics of Read Only Memory (ROM) and Erasable Programmable Read Only Memory (EPROM) in microprocessor architecture.
