Answer to several people, please read to the bottom of this message.

Hi, Ben !
I cannot go to www.wisclub.net, it seem the address does not exist. But from Ben Zijlstra, I have try Sam's site in http://www.homepages.hetnet.nl/~sbergman.../index.htm. Tt works.
About the crystal clock, is it possible if i'm using 20 Mhz (due to the maximum clock frequency of the AT89C51/52 20PC) ?
Is it possible if the slave clock will be various, one using 12Mhz anothers using 20Mhz, with the master using the fastest clock : 24 Mhz so that the master can adjust itself to any speed the slave capability ?

Thank's in advance !


Hi, Erik Malund !
Thank's for your help.
I think I'm using VB just in the making of user interface program running under Windows. The Microcontroller itself will be programmed using assembly language. I'm using ASM51 assembler. I have using it all the time. But honestly, I'm lack of expirience in serial programming algorithm.

I think you right, but for now i'll use one master for a while, when more than 16 slaves (as you suggest) need to be attach to the bus, I'll add more master.

About your solution "using '51 master controlling slaves and communicate to PC, I aggree with you. By doing this way, I think the PC would not be burdensome on controlling all slave, that's why I'm choosing VB to do just to graphicaly interface the computer operator to monitor the bus's activities e.g : how many message, collision, and monitor the condition of each slave's micros on doing each own job (e.g : one micro controlling temperature of a machine by controlling the speed of a fan, sending the temperature and RPM at the present; another micro controlling moving sign display of LEDs, and etc). Is this true, that the VB programmed program on PC don't have to be sophisticated ?

What checksum do you suggest me to make ? Like odd or even parity ?

Thank you.



Hi Cory Spackman !
Which one do you suggest me to use ?
(CRC8 or CRC16 ?)
Thank You!


Hi Sanjay Ahuja !
I'll try to learn the Mscomm function.
Thank you