SP303 Datasheet, PDF (7/8 Pages) Sipex Corporation – RS232/AppleTalk TM Serial Transceiver

the transmit data driver in ApppleTalk™ mode.
Both differential drivers have output signals on
each pin that typically swing ±6V. The peak to
peak differential voltage swing is typically ±12V.
The second driver is used for transmitting the
handshake output signal and can be used as
either a differential driver or single ended. This
particular application required a single–ended
inverting signal for the handshake output signal.
Some Macintosh equipment requires an extra
single–ended inverting receiver which is called
a general purpose input. The GPI receiver is
normally connected to pin 7 on the external 8 pin
connector. This receiver is not available on the
SP303CT.
Since the SP303CT is usually connected to the
outside world, it is suggested that the user place
transient voltage suppression devices on each of
the 1/0 lines to ensure up to ±25kV ESD protec-
tion.
POWER SUPPLY SEQUENCING
There are two requirements for power supply
sequencing for the SP303. The first is that V_DD
is always greater than V_CC. The second is that
when the part is powered up, V_DD must be
applied 20ms before V_CC.
RTS
TXD
RXD
CTS
DTR
RTS
TXD
RXD
CTS
DTR
SUPPLY
+5V +12V –12V
28 1 15
7
VCC VDDVEE
SELECT A
8 _{SELECT B}
22
6
23
5
26
2
3
SP303
17
12
13
9
20
10
14 _GND
SUPPLY
+5V +12V –12V
28 1 15
7
VCC VDDVEE
SELECT A
8 _{SELECT B}
22
6
23
5
26
2
3
SP303
17
12
13
9
20
10
14 _GND
RFI FILTER ^TXDA–
TXDA+
RFI FILTER
RFI FILTER ^RXDA+
RFI FILTER
RXDA–
RFI FILTER ^HSKiA
RFI FILTER ^HSKoA
No Connect
876
5
43
21
RFI FILTER ^TXDA–
TXDA+
RFI FILTER
RFI FILTER ^RXDA+
RFI FILTER
RXDA–
RFI FILTER ^HSKiA
RFI FILTER ^HSKoA
No Connect
876
5
43
21
Figure 4. Macintosh™ AppleTalk™ Interface.
Corporation
SIGNAL PROCESSING EXCELLENCE
75