Data transfer schemes of 8085 microprocessor
Here we can see data transfer schemes of 8085 microprocessor. In 8085 microprocessor based systems several input and output devices are connected. We know that data transfer may take place between microprocessor and memory, microprocessor and I/O devices and memory & I/O devices. As we know not much of the problems arise for the data communication between microprocessor and memory as same technology is used in the manufacturing of memory and microprocessor.
The main reason for that the speed of the memory is almost compatible with the speed of 8085 microprocessor. Now the main concern is for the data transfer between the microprocessor and I/O devices. The main problems arise due to mismatch of the speed of the I/O devices and the speed of microprocessor or memory. To overcome this problem of speed mismatch between the microprocessor and I/O devices we have to do something. For that reason only we introduce data transfer schemes of 8085 microprocessor. So following data transfer schemes may be considered for smooth data transfer process. The data transfer schemes of 8085 microprocessor were categorised depending upon the capabilities of I/O devices for accepting serial or parallel data.
The 8085 microprocessor is a parallel device. That means it transfers eight bits of data simultaneously over eight data lines (parallel I/O mode). However in many situations, the parallel I/O mode is either impractical or impossible. For example, parallel data communication over a long distance becomes very expensive. Similarly, parallel data communication is not possible with devices such as CRT terminal or Cassette tape etc.
Serial I/O mode transfer
For these devices and for these reasons serial I/O mode is used. In serial I/O mode transfer a single bit of data on a single line at a time. For serial I/O data transmission mode, 8-bit parallel word is converted to a stream of eight serial bit using parallel-to-serial converter. Similarly, in serial reception of data, the microprocessor receives a stream of 8-bit one by one which are then converted to 8- bit parallel word using serial-to-parallel converter. For this purpose data transfer schemes of 8085 microprocessor are introduced.
Parallel data transfer scheme
Parallel data transfer scheme is faster than serial I/O transfer. in parallel data transfer 8-bit data send all together with 8 parallel wire. In 8085 microprocessor mainly three types of parallel data transfer scheme we observed. Those are
- Programmed I/O Data Transfer
- Interrupt Driven I/O Data Transfer
- Direct Memory Access (DMA) Data Transfer.