Hi Paul,
In its true sense RS232 is an asynchronous port, which means that the data sent is not clocked but at a fixed rate which is the baud rate. You can use hand shake protocols or use Start pattern and end pattern to read the data in and out. All communication is ascii based.
Having said that, there is a way to assert or de-assert some of the lines on the serial Port. Drop a Property node then right click and Select Class->Visa->I/O Session->Serial Instr. Again right Click and Select Properties->Modem Line Settings and then you can see the lines available to you. You will have to do the assert and deassert this way. It can do some lines and logic is not TTL, so you will have to check your interface.
If I were you, I would instead choose the Parallel Port and use In and Out Port VI's. The parallel port has three address. Most common are 0x378 = Control, 0x379 = Status, 0x380 = Data. Using these ports you can read / Write data bit by bit Synchronously if you desire. With LV 7.1 this functionality is now standard as the CVI driver is included.
One suggestion, is if you use the parallel port, I suggested you put a simple buffer like an inverter (7404?) in between the PC Parallel Port and your Device. This is to protect, as well as have full TTL/CMOS capability to drive your device.
Currently I am using Parallel Port for I2C communication which is two wire Clock/Data lines and the information is transferred bit wise physically and byte wise in Software.
So you may use either, If you need more details, Please post with specific question and I am sure Someone here will be of help
Good Luck!
Mache
