MC68331TS datasheet(66/84 Pages) FREESCALE

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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

SCBR

RESET:

Freescale Semiconductor, Inc.

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