Computer Interfacing & Related Issues

TRANSMISSION MODES (based on timing)• Asynchronous• Synchronous

TRANSMISSION MODES (based on data sequence / rate)  • Serial • Parallel

• Asynchronous – used exclusively in serial data transmission.  Does not use a common clock signal to synchronize. The recipient recognizes the data using the start and stop bits, and the coding system used.

• Synchronous – A clock signal is incorporated into the data lines.  Used exclusively in parallel data transmission.

• Serial – Data bits are sent along one line, in a sequential manner.  Low overall transmission speeds.  Low hardware requirements.  

• Parallel – All the bits are sent together, along with a synchronizing clock pulse.  Faster data transmission rates, shorter distances, higher hardware requirement.

Parallel data transmission (Data Bus):

Computer and microcontroller systems

A generalized view of a computer system

Microcontrollers

Different ‘PORTS’ used in computer communication

Physical Ports

Data Transfer with an External Device

Timing Diagrams

Ways to initiate and synchronize data acquisition:

•Software trigger status poll method•Hardware trigger status poll method•Hardware trigger DMA•Embedded processor method (separate DAQ card)

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