Chapter 14 Serial Communications Interface (S08SCIV4)
MC9S08SG32 Data Sheet, Rev. 7
Freescale Semiconductor
211
14.2.4
SCI Status Register 1 (SCIS1)
This register has eight read-only status ags. Writes have no effect. Special software sequences (which do
not involve writing to this register) are used to clear these status ags.
3
TE
Transmitter Enable
0 Transmitter off.
1 Transmitter on.
TE must be 1 in order to use the SCI transmitter. When TE = 1, the SCI forces the TxD pin to act as an output
for the SCI system.
When the SCI is congured for single-wire operation (LOOPS = RSRC = 1), TXDIR controls the direction of
trafc on the single SCI communication line (TxD pin).
TE also can be used to queue an idle character by writing TE = 0 then TE = 1 while a transmission is in progress.
When TE is written to 0, the transmitter keeps control of the port TxD pin until any data, queued idle, or queued
break character nishes transmitting before allowing the pin to revert to a general-purpose I/O pin.
2
RE
Receiver Enable — When the SCI receiver is off, the RxD pin reverts to being a general-purpose port I/O pin.
If LOOPS = 1 the RxD pin reverts to being a general-purpose I/O pin even if RE = 1.
0 Receiver off.
1 Receiver on.
1
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 signicant data bit in a character
(WAKE = 1, address-mark wakeup). Application software sets RWU and (normally) a selected hardware
0 Normal SCI receiver operation.
1 SCI receiver in standby waiting for wakeup condition.
0
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 (13 or 14 if BRK13 = 1) 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
0 Normal transmitter operation.
1 Queue break character(s) to be sent.
76543210
R
W
Reset
11000000
= Unimplemented or Reserved
Figure 14-8. SCI Status Register 1 (SCIS1)
Table 14-4. SCIC2 Field Descriptions (continued)
Field
Description