Under what conditions does blocking occur when using a buffered channel in a data transfer system?

In Go, a buffered channel blocks in two main cases:

1. When sending (writing) to the channel: if the channel's buffer is full (i.e., the number of elements in the channel has reached its capacity), then attempting to send a new value blocks the goroutine until someone reads from the channel and frees up space.

2. When reading from the channel: if the channel is empty (no elements to read), then attempting to read from the channel blocks the goroutine until someone sends a new value.

Thus, blocking occurs when trying to send data to a full buffer or when trying to read from an empty buffer.