Datasheet
66 MC68331TS/D
*A rate of 64 baud is not available with a 20.97-MHz system clock. To achieve this rate, the SYNCR can be pro-
grammed to generate a lower system clock rate.
SCCR1 contains SCI configuration parameters. The CPU can read and write this register at any time.
The SCI can modify RWU in some circumstances. In general, interrupts enabled by these control bits
are cleared by reading SCSR, then reading (receiver status bits) or writing (transmitter status bits)
SCDR.
Bit 15 — Not Implemented
LOOPS — Loop Mode
0 = Normal SCI operation, no looping, feedback path disabled
1 = Test SCI operation, looping, feedback path enabled
LOOPS controls a feedback path on the data serial shifter. When loop mode is enabled, SCI transmitter
output is fed back into the receive serial shifter. TXD is asserted (idle line). Both transmitter and receiver
must be enabled before entering loop mode.
WOMS — Wired-OR Mode for SCI Pins
0 = If configured as an output, TXD is a normal CMOS output.
1 = If configured as an output, TXD is an open-drain output.
WOMS determines whether the TXD pin is an open-drain output or a normal CMOS output. This bit is
used only when TXD is an output. If TXD is used as a general-purpose input pin, WOMS has no effect.
ILT — Idle-Line Detect Type
0 = Short idle-line detect (start count on first one)
1 = Long idle-line detect (start count on first one after stop bit(s))
Table 25 SCI Baud Rates
Nominal Baud Rate Actual Rate with
16.78-MHz Clock
SCBR Value Actual Rate with
20.97-MHz Clock
SCBR Value
64* 64.0 $1FFF — —
110 110.0 $129E 110.0 $1745
300 299.9 $06D4 300.1 $0888
600 599.9 $036A 600.1 $0444
1200 1199.7 $0165 1200.3 $0222
2400 2405.0 $00DA 2400.6 $0111
4800 4810.0 $006D 4783.6 $0089
9600 9532.5 $0037 9637.6 $0044
19200 19418.1 $0016 19275.3 $0022
38400 37449.1 $000E 38550.6 $0011
76800 74898.3 $0007 72817.8 $0009
Maximum Rate 524288.0 $0001 655360.0 $0001
SCCR1 — SCI Control Register 1 $YFFC0A
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 SCBR
RESET:
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc
.
..