The bus cycle is also named as machine cycle. Bus cycle of 8086 is used to access memory, peripheral devices (Input/Output devices), and Interrupt controller. Bus cycle corresponds to a sequence of events that starts with an address being output on system address bus followed by a write or read data transfer. During these operations, a series of control signals are also produced by microprocessor to control direction and timing of bus.
There are at least four clock periods in a bus cycle of 8086 microprocessor. These four clock periods are called T1, T2, T3 and T4 states.
These four clock states gives bus cycle duration T of 200 ns *4 = 800 ns in 5-MHz 8086 system.
- Read Cycle :
When a read cycle is to be performed, during T1 microprocessor puts an address on address bus, and then bus is put in high impedance state during T2 state. Data to be read must be out on bus during T3 and T4. During T3 bus is made “reserved for data in” and finally data is read during T4.
- Write Cycle :
In case of write memory cycle, during T1 state microprocessor puts an address on address bus. Data is put on data bus by CPU during T2 state and maintained during T3 and T4 states, that is written out to memory or I/O devices.
Attention reader! Don’t stop learning now. Get hold of all the important CS Theory concepts for SDE interviews with the CS Theory Course at a student-friendly price and become industry ready.
- Difference between Single Bus Structure and Double Bus Structure
- Bus organization of 8085 microprocessor
- Flag register of 8086 microprocessor
- General purpose registers in 8086 microprocessor
- Arithmetic instructions in 8086 microprocessor
- Logical instructions in 8086 microprocessor
- Data transfer instructions in 8086 microprocessor
- Reset Accumulator (8085 & 8086 microprocessor)
- Process control instructions in 8086 microprocessor
- Memory Segmentation in 8086 Microprocessor
- Differences between 8085 and 8086 microprocessor
- Addressing modes in 8086 microprocessor
- String manipulation instructions in 8086 microprocessor
- Program execution transfer instructions in 8086 microprocessor
- Pin diagram of 8086 microprocessor
- Interrupts in 8086 microprocessor
- Computer Organization | Different Instruction Cycles
- BUS Arbitration in Computer Organization
- System Bus Design
- Three-State Bus Buffers
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.