The term is not familiar to me. In talking about a UART, framing refers to how the bits in a serial data stream are organized. A common framing method is referred to as 8N1, which stands for 8 data bits, no parity bit, and 1 stop bit. All UART framing methods include an initial START bit so the mention of it does not need to be included. The total length of a frame in 8N1 is 10 bits consisting of: