Philips Semiconductors

Product specification

SCN68681

Dual asynchronous receiver/transmitter (DUART)

1998 Sep 04

11

Table 2.

Register Bit Formats

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

MR1A

RxRTS

CONTROL

RxINT

SELECT

ERROR

MODE*

PARITY MODE

PARITY

TYPE

BITS PER

CHARACTER

MR1A

MR1B

0 = No

1 = Yes

0 = RxRDY

1 = FFULL

0 = Char

1 = Block

00 = With Parity

01 = Force Parity

10 = No Parity

11 = Multidrop Mode

0 = Even

1 = Odd

00 = 5

01 = 6

10 = 7

11 = 8

NOTE:

*In block error mode, block error conditions must be cleared by using the error reset command (command 4x) or a receiver reset.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

MR2A

CHANNEL MODE

TxRTS

CONTROL

CTS

ENABLE Tx

STOP BIT LENGTH*

MR2A

MR2B

00 = Normal

01 = Auto-Echo

10 = Local loop

11 = Remote loop

0 = No

1 = Yes

0 = No

1 = Yes

0 = 0.563

4 = 0.813

8 = 1.563

C = 1.813

1 = 0.625

5 = 0.875

9 = 1.625

D = 1.875

2 = 0.688

6 = 0.938

A = 1.688

E = 1.938

3 = 0.750

7 = 1.000

B = 1.750

F = 2.000

NOTE:

*Add 0.5 to values shown for 0 - 7 if channel is programmed for 5 bits/char.

CSRA

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

CSRA

CSRB

RECEIVER CLOCK SELECT

TRANSMITTER CLOCK SELECT

CSRB

See Text

See Text

NOTE:

* See Table 6 for BRG Test frequencies in this data sheet, and “Extended baud rates for SCN2681, SCN68681, SCC2691, SCC2692,

SCC68681 and SCC2698B” in application notes elsewhere in this publication

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

CRA

CRB

MISCELLANEOUS COMMANDS

DISABLE Tx

ENABLE Tx

DISABLE Rx

ENABLE Rx

CRB

Not used –

should be 0

See Text

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

NOTE:

*Access to the upper four bits of the command register should be separated by three (3) edges of the X1 clock. A disabled transmitter cannot

be loaded.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

SRA

SRB

RECEIVED

BREAK*

FRAMING

ERROR*

PARITY

ERROR*

OVERRUN

ERROR

TxEMT

TxRDY

FFULL

RxRDY

SRB

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

NOTE:

*These status bits are appended to the corresponding data character in the receive FIFO. A read of the status provides these bits (7:5) from the

top of the FIFO together with bits (4:0). These bits are cleared by a “reset error status” command. In character mode they are discarded when

the corresponding data character is read from the FIFO. In block error mode, block error conditions must be cleared by using the error reset

command (command 4x) or a receiver reset.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

OP7

OP6

OP5

OP4

OP3

OP2

OPCR

0 = OPR[7]

1 = TxRDYB

0 = OPR[6]

1 = TxRDYA

0 = OPR[5]

1 = RxRDY/

FFULLB

0 = OPR[4]

1 = RxRDY/

FFULLA

00 = OPR[3]

01 = C/T OUTPUT

10 = TxCB(1x)

11 = RxCB(1x)

00 = OPR[2]

01 = TxCA(16x)

10 = TxCA(1x)

11 = RxCA(1x)

OPR

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

OPR bit

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

OP pin

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

NOTE:

The level at the OP pin is the inverse of the bit in the OPR register.