When Non-blocking mode is enabled, reads from the channel will return 0 instead of waiting if a complete message has not yet been received. Writes to the channel will return 0 instead of waiting if there is not enough room in the transmit buffer to store the entire message.

An important note for non-blocking HDLC read operations is that the library does store partial messages in the application's buffer space. The partial message data must be preserved for future reads from the channel. This means that the application program should maintain buffers for each channel to be read.

Under certain conditions the embedded code was not clearing its "out of sync" flag if the host application read all the valid data from a channel whose framer went out of sync. If this situation occurred, the embedded channelization code would not resume collecting data when the framer came back into sync and subsequent calls to pci_read_chan would result in an ETIMEDOUT error.

This means that compiling user applications no longer requires that macro to be defined on the compiler's command line.