A field used in conjunction with the format (FO) bit to specify the word length of the buffered serial port (BSP) transmitter and receiver. When FO = FE = 00, the format is 16-bit words; when FO = FE = 01, the format is 10-bit words; when FO = FE = 10, the format is 8-bit words; and when FO = FE = 11, the format is 12-bit words. For 8-,10-, and 12-bit words, the received words are right-justified and the sign bit is extended to form a 16-bit word. The words to transmit must be right-justified. At reset, FE = 0. This bit is stored in the BSP control extension register (SPCE).