7 Questions
Describe the bus systems used in computers and their purpose.
a common group of wires that interconnects components in a computer system address bus, control bus, data bus
If a memory write cycle takes 50ns, how long will it take writing 1024 x 768 bytes data array to the memory? How many times can this be done in one second?
25
List three broad classifications of external, or peripheral, devices.
human readable, machine readable, communication
What is the difference between memory mapped IO and isolated IO?
MMIO, integration and efficiency are crucial PMIO, simplicity and strict separation of I/O memory operations are beneficial
When DMA module takes control of a bus, what does the processor do?
burst mode, cycle stealing
On a typical microprocessor, a distinct I/O address is used to refer to the I/O data registers and a distinct address for the control and status registers in an I/O controller for a given device. Such registers are referred to as ports. In the Intel 8088, two I/O instruction formats are used. In one format, the 8-bit opcode specifies an I/O operation; this is followed by an 8-bit port address. Other I/O opcodes imply that the port address is in the 16-bit DX register. How many ports can the 8088 address in each I/O addressing mode?
2 to the power of 8 and 2 to the power of 16
We would like to interface a peripheral device (UART 16550) to intel 8088 microprocessor. Base address of the device is decided as 300h
What is the purpose of UART peripheral device?
to facilitate serial communication between devices
Study Notes
Bus Systems in Computers
- A bus is a communication pathway that allows different components of a computer to exchange data
- Bus systems are used to connect and communicate between CPU, memory, and peripherals
Memory Write Cycle
- Time taken to write 1024 x 768 bytes of data to memory: 1024 x 768 = 786,432 bytes
- Writing 786,432 bytes with a 50ns memory write cycle: 50ns x 786,432 = 39,321,600 ns ≈ 39.32 ms
- Number of times this can be done in one second: 1 s ÷ 39.32 ms ≈ 25.45 times
Classification of External Devices
- Three broad classifications of external, or peripheral, devices: input devices, output devices, and storage devices
Memory Mapped IO vs Isolated IO
- Memory-mapped I/O: I/O devices are assigned memory addresses, and data is transferred using memory access instructions
- Isolated I/O: I/O devices have separate address spaces and require specialized I/O instructions
DMA Module
- When a DMA module takes control of a bus, the processor is idle and waits for the DMA operation to complete
I/O Addressing in Intel 8088
- Two I/O instruction formats: one using an 8-bit opcode and an 8-bit port address, another using an opcode that implies the port address is in the 16-bit DX register
- Number of ports addressable in each I/O addressing mode: 256 in the first format, and 65,536 in the second format
Interfacing a Peripheral Device
- Purpose of UART (Universal Asynchronous Receiver-Transmitter) peripheral device: enables serial communication with a device
- UART 16550 device base address: 300h
Learn about the different bus systems used in computers, including their functions and purposes. Understand how data is transmitted and shared between components in a computer system.
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