MC68HC05B6_13 Datasheet, PDF (83/302 Pages) Freescale Semiconductor, Inc – Microcontrollers

R8 — Receive data bit 8
This read-only bit is the ninth serial data bit received when the SCI system is configured for nine
data bit operation (M = 1). The most significant bit (bit 8) of the received character is transferred
into this bit at the same time as the remaining eight bits (bits 0–7) are transferred from the serial
receive shifter to the SCI receive data register.
T8 — Transmit data bit 8
This read/write bit is the ninth data bit to be transmitted when the SCI system is configured for nine
data bit operation (M = 1). When the eight low order bits (bits 0–7) of a transmit character are
transferred from the SCI data register to the serial transmit shift register, this bit (bit 8) is
transferred to the ninth bit position of the shifter.
M — Mode (select character format)
The read/write M-bit controls the character length for both the transmitter and receiver at the same
time. The 9th data bit is most commonly used as an extra stop bit or it can also be used as a parity
6
bit (see Table 6-1).
1 (set) – Start bit, 9 data bits, 1 stop bit.
0 (clear) – Start bit, 8 data bits, 1 stop bit.
Table 6-1 Method of receiver wake-up
WAKE M
0
x
1
0
1
1
x = Don’t care
Method of receiver wake-up
Detection of an idle line allows the next data type received to cause the receive
data register to fill and produce an RDRF flag.
Detection of a received one in the eighth data bit allows an RDRF flag and
associated error flags.
Detection of a received one in the ninth data bit allows an RDRF flag and
associated error flags.
WAKE — Wake-up mode select
This bit allows the user to select the method for receiver wake-up. The WAKE bit can be read or
written to any time. See Table 6-1.
1 (set) – Wake-up on address mark; if RWU is set, SCI will wake-up if the 8th
(if M=0) or 9th (if M=1) bit received on the Rx line is set.
0 (clear) – Wake-up on idle line; if RWU is set, SCI will wake-up after 11 (if M=0)
or 12 (if M=1) consecutive ‘1’s on the Rx line.
MC68HC05B6
Rev. 4.1
SERIAL COMMUNICATIONS INTERFACE
Freescale
6-11