Corporation

SIGNAL PROCESSING EXCELLENCE

74

Figure 3. RS-232 Interface.

SP303CT is usually connected to the outside

world, it is suggested that the user place tran-

sient voltage suppression devices on each of the

I/O lines to ensure up to

±25kV ESD protection.

While the part is programmed for RS-232 mode,

the drivers and receivers can operate up to

200kbps. The RS-232 receiver inputs are ca-

pable of receiving signals up to

±30V. The

Macintosh™ AppleTalk™ mode inputs and

outputs are protected to guard against the situa-

tion where an RS-232 cable is connected to the

port while it is configured for AppleTalk™

mode.

APPLICATION EXAMPLE

MACINTOSH™ APPLETALK™ SERIAL

INTERFACE

Figure 4 shows the SP303CT programmed for

Macintosh™ AppleTalk™ operating mode. In

this mode the SP303CT offers one differential

driver used for transmitting data, one differen-

tial receiver used for receiving data, one single–

ended, non–inverting receiver used to receive a

handshake signal, and one single–ended invert-

ing driver used to transmit a handshake signal.

The differential driver used for transmitting

data can be put into tri–state mode by bringing

the TxEN line high; a low on this pin will enable

the driver output. This function only applies to

GND

SUPPLY

+5V +12V –12V

SELECT

A

B

T1

T2

T3

T4

R1

R2

R3

R4

VCC VDD VEE

SP303

28

1

15

23

6

24

5

20

9

19

10

26

3

27

2

17

12

16

13

14

7

8

TXD

RTS

DCD

DSR

RXD

CTS

DTR

RFI FILTER

TXD

RTS

DCD

DSR

RXD

CTS

DTR

3

4

5

87

6

1

2

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER

GND

SUPPLY

+5V +12V –12V

SELECT

A

B

T1

T2

T3

T4

R1

R2

R3

R4

VCC VDD VEE

SP303

28

1

15

23

6

24

5

20

9

19

10

26

3

27

2

17

12

16

13

14

7

8

TXD

RTS

DCD

DSR

RXD

CTS

DTR

RFI FILTER

TXD

RTS

DCD

DSR

RXD

CTS

DTR

3

4

5

87

6

1

2

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER

RFI FILTER