If you want to communicate with an external device using an exchange of signals to request and acknowledge each data transfer, use handshaking.
For example, you might want to acquire an image from a scanner. The process involves the following steps:
The scanner sends a pulse to your measurement device after it scans the image and is ready to transfer the data.
Your measurement device reads an 8-, 16-, or 32-bit digital sample.
Your measurement device then sends a pulse to the scanner to inform the scanner that the digital sample has been read.
The scanner sends out another pulse when the scanner is ready to send another digital sample.
After your measurement device receives this digital pulse, the device reads the sample.
This process repeats until all the samples are transferred.
Not all devices support handshaking. Refer to your device documentation to see if handshaking is supported on your device. For E Series devices, only those devices with more than eight digital lines—those devices that have an additional 8255 chip onboard—support handshaking.