SERIAL COMMUNICATION INTERFACE (SCI)
6 - 14
PORT C
MOTOROLA
6.3.2.1
SCI Control Register (SCR)
The SCR is a 16-bit read/write register that controls the serial interface operation. Each
bit is described in the following paragraphs.
6.3.2.1.1
SCR Word Select (WDS0, WDS1, WDS2) Bits 0, 1, and 2
The three word-select bits (WDS0, WDS1, WDS2) select the format of the transmit and re-
ceive data. The formats include three asynchronous, one multidrop asynchronous mode,
and an 8-bit synchronous (shift register) mode. The asynchronous modes are compatible
with most UART-type serial devices and support standard RS232C communication links.
23
16 15
8 7
0
X:$FFF6
X:$FFF5
X:$FFF4
SRX
SRX
SRX
SCI RECIEVE DATA REGISTER HIGH (READ ONLY)
SCI RECIEVE DATA REGISTER MID (READ ONLY)
SCI RECEIVE DATA REGISTER LOW (READ ONLY)
RXD
SCI RECEIVE DATA SHIFT REGISTER
NOTE: SRX is the same register decoded at three different addresses.
23
16 15
8 7
0
23
16 15
8 7
0
X:$FFF6
X:$FFF5
X:$FFF4
STX
STX
STX
SCI TRANSMIT DATA REGISTER HIG (WRITE ONLY)
SCI TRANSMIT DATA REGISTER MID (WRITE ONLY)
SCI TRANSMIT DATA REGISTER LOW (WRITE ONLY)
TXD
SCI TRANSMITDATA SHIFT REGISTER
NOTES:
1.
Bytes are masked on the fly.
2.
STX is the same register decoded at three different addresses.
STXA
X:$FFF3
SCI TRANSMITDATA ADDRESS REGISTER
(WRITE ONLY)
(a) Receive Data Register
(b) Transmit Data Register
Figure 6-9 SCI Programming Model
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Freescale Semiconductor, Inc.
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