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Computer Control : 

Computer Control Parallel & Serial Port Communication

PC Parallel Port - Features : 

PC Parallel Port - Features Commonly known as the printer port 25 pin D-Type connector It has 12 digital output pins, 5 digital input pins Pins operate at the TTL voltage level i.e. 0 – 5V Port identified by a base address in the computer I/O memory space

PC Parallel Port – Pin Layout : 

PC Parallel Port – Pin Layout

PC Parallel Port – I/O Registers : 

PC Parallel Port – I/O Registers Most PC’s have 378 Hex base address 8 output pins are accessed via the DATA port (Base address) 4 output pins are accessed via the CONTROL port (Base address + 2) 5 input pins are accessed via the STATUS port (Base address + 1)

PC Serial Port - Features : 

PC Serial Port - Features Most commonly 9 pin D-Type connector. 25 pin D-Type is rare Pins operate at -25 to + 25 voltage levels Data transmitted as a bit sequence Known as the EIA RS232C port or simply RS232

EIA RS232C Specifications : 

EIA RS232C Specifications Logic 0 is between +3 to +25 volts Logic 1 is between -3 to -25 volts -3 to +3 volts region is undefined Maximum data rate of 19,600 bps

Serial Port vs. Parallel Port : 

Serial Port vs. Parallel Port Serial cables can be much longer that Parallel cables 50V swing compared to 5V swing Serial suited for wireless transmission Microcontrollers just need two pins (RXD & TXD) for communication

RS-232 Level Converters : 

RS-232 Level Converters For using the RS232 data, digital devices need TTL/CMOS voltage levels Level conversion is done using IC MAX232 / DS232

RS-232 frame decoding : 

RS-232 frame decoding The decoding of the bit sequence frame is done by computer hardware When communicating with robots, decoding done by onboard microcontroller Microcontroller Serial communication interface is known as UART (Universal Asynchronous Receiver Transmitter)

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