>>>>I am facing problems writing "Serial Communication" routines under Windows.I am trying these routines since last few months and with my experience, I have come accross foll Conclusions/problems
>>>>
>>>
>>>Narendra
>>>
>>>The market seems to definitely be moving towards Windows & away from DOS. Going to DOS will find you in a shrinking market.
>>>
>>>There are COMM utilities out the like SilverFox from SilverWare and others that will support the 16 bit environment. Plus eliminate a tedious learning curve. Look in the trade magazines for such products.
>>>
>>>Tom
>>
>>Thanks Tom but my problem is different. I have to write the
>>routines bcz I am reading data from the device which has its own
>>protocol & handshking that too very fast.I have to respond to
>>each char received on port, (For example device first send ENQ
>>then I reply with ACK, then it sends block of 4 chars, then i
>>respond, then it sends header etc...). In this case I need a
>>utility/OCX which is so fast & powerful that it generates
>>interrupt as soon as char arrives at port.
>>
>>I tried MSCOMM16.OCX with VB4.0, it just does not work for me.and I don't think any utility can do this, bcz being a multitasking env,
>>Windows does not give highest priority to COM port (ie a char
>>just arrived at port & windows starts swaping between HDD & RAM,
>>you can't do anything at this time). Its OK if
>>you want to upload/download a large file in which case time is
>>not that much critical.
>>If you have come across any utility which is 100% perfect for
>>these type of application,please reply soon.
>
>Narendra
>
>The only way to handle this is with a clever buffering scheme. Some products (the more effective) actually use a 3 part buffering scheme; The UART buffer, a low level buffer & a user buffer. You should be able to get away with 2 at the most; the UART buffer & maybe a low level buffer. Just watch the size of your buffers. Don't try to read each char from the port but read it from the buffers.
>
>HTH,
>Tom

Ya Tom,I have tried with buffering(size ranging from 10 bytes
to 30000), but in some cases, if I don't read char by char & give reply in time to the device, it generates an error & starts negative response. In this case I face more trouble. To give u an example say device sends ENQ & then waits for some
time (say few milisecs), now during this if I don't give answer
It again sends ENQ, so now if I read from buffer one char & reply the second char is also ENQ, where as for me after I send a reply it should be STX). Also I have to perform Check sums etc on the data.

Narendra