MC9S08GB60 Datasheet, PDF (181/290 Pages) Motorola, Inc – Microcontrollers

SCI Registers and Control Bits
RE — Receiver Enable
When the SCI receiver is off, the RxD1 pin reverts to being a general-purpose port I/O pin.
1 = Receiver on.
0 = Receiver off.
RWU — Receiver Wakeup Control
This bit can be written to 1 to place the SCI receiver in a standby state where it waits for automatic
hardware detection of a selected wakeup condition. The wakeup condition is either an idle line between
messages (WAKE = 0, idle-line wakeup), or a logic 1 in the most significant data bit in a character
(WAKE = 1, address-mark wakeup). Application software sets RWU and (normally) a selected
hardware condition automatically clears RWU. Refer to Section 11.6.3, “Receiver Wakeup
Operation,” for more details.
1 = SCI receiver in standby waiting for wakeup condition.
0 = Normal SCI receiver operation.
SBK — Send Break
Writing a 1 and then a 0 to SBK queues a break character in the transmit data stream. Additional break
characters of 10 or 11 bit times of logic 0 are queued as long as SBK = 1. Depending on the timing of
the set and clear of SBK relative to the information currently being transmitted, a second break
character may be queued before software clears SBK. Refer to Section 11.5.2, “Send Break and
Queued Idle,” for more details.
1 = Queue break character(s) to be sent.
0 = Normal transmitter operation.
11.10.4 SCI x Status Register 1 (SCIxS1)
This register has eight read-only status flags. Writes have no effect. Special software sequences (that do
not involve writing to this register) are used to clear these status flags.
Bit 7
6
5
4
3
2
Read: TDRE
TC
RDRF IDLE
OR
NF
Write:
Reset: 1
1
0
0
0
0
= Unimplemented or Reserved
Figure 11-9. SCI x Status Register 1 (SCIxS1)
1
Bit 0
FE
PF
0
0
TDRE — Transmit Data Register Empty Flag
TDRE is set out of reset and when a transmit data value transfers from the transmit data buffer to the
transmit shifter, leaving room for a new character in the buffer. To clear TDRE, read SCIxS1 with
TDRE = 1 and then write to the SCI data register (SCIxD).
1 = Transmit data register (buffer) empty.
0 = Transmit data register (buffer) full.
MC9S08GB/GT Data Sheet, Rev. 2.3
Freescale Semiconductor
181