SERIAL PORT

[manmohan]

PLS HELP ME IN INTERFACING COM1/COM2 (SERIAL PORTS )
THROUGH QB45(QUICK BASIC)
HOW TO CONFIGURE THE PORTS FOR COMMUNICATION.
MANMOHAN

[Kevin Weddle]

Look on the internet for a null modem cable. Then use the example program that comes with the IDE. After that, just experiment with the lines until you get the desired result. I know, the lines can be confusing. But remember it is intentional design of the communication system so there is no need to worry because you can't know what the design is.

[prateeksikka]

be careful to use the statement outport address once and inport statement twice to handle the problem of repeated readings in quick basic(a serious flaw in qb not C)
PRATEEK

[Shahriar]

Remember Two things:

1- Always connect your PC serial port directly to a buffer IC (i.e. 74245) because PC serial port is not protected from short circuit.

2- the other thing that many people forget is that the address of PC ports are in HEX, for example 370H, many people mistake it with decimal and misspell the "H" or "0x"

HTH - Shahriar

[MP]

I build a lot of equipment which uses the serial port. I have shorted the pins of the computer port many times with no incident. I have never in many years had or seen such a problem. Connection of pins 2,3 and 5 directly to equipment is safe. It is when you have one of the low powered laptops that you have a problem. They do not use standard levels. The higher levels of your connected equipment can cause them harm.

MP

[Shahriar]

Dear MP

Is it also true with LPT1 port. I mean:
Is "Parallel port" short circuit protected too? I do not dare to check it out.

Shahriar

[MP]

On a parallel port:
Data bits D0-D7 connect directly to an octal tri state latch and an octal tri state buffer. These are 74LS374 and 74LS244. Pins 2 through 9)
The Ack, Busy, PE, Select and Error, pins 10, 11, 12, 13, 15, go to another tri state buffer. The ack line also connets to IRQ7, Pin B27 of the ISA bus. As you can see, the only line that is not buffered is the one going to IRQ7.
However, it is always possible to pump enough high voltage into the port to burn the buffer chips or to burn a trace on the board.
This is the same concern one might have with a serial port. One could certainly connect enough high voltage to the pins to take out the buffer or traces. This is the reason many designers will use isolation. Personally, I do not think you make anything "idiot proof" enough to cover everything that the end user might do to your product, so I do not add all the extras to peripherals that I design. I make a disclaimer regarding responsibility and warranty.

MP

[prateeksikka]

hi MP!
AND OTHERS
I NUST ADD THAT BE CAREFUL TO CLEAR THE DATE AON THE PORTS BEFORE USING ANY INPORT COMMAND IN YOUR PROGRAM,AN EXCESSIVELY HIGH VOLTAGE PRESENT ON A PORT PIN ALONG WITH THIS CARELESSNESS CAN EVEN DAMAGE YPUR MOTHERBOARD(IT IS A PRACTICAL EXPERIENCE)
PRATEEK