SP504 Datasheet, PDF (29/32 Pages) Sipex Corporation – WAN Multi-Mode Serial Transceiver

Additional transceivers
with the SP504
Serial ports usually can have two data sig-
nals (SD, RD), three clock signals (TT, ST,
RT), and at least eight control signals (CS,
RS, etc.). EIA-RS-449 contains twenty six
signal types for a DB-37 connector. A DB-
37 serial port design may require thirteen
drivers and fourteen receivers¹. Although
many applications do not use all these
signals, some applications may need to
support extra functions such as diagnostics.
The SP504 supports enough transceivers
for the primary channels of data, clock and
control signals. Configuring LL, RL and TM
would require two additional drivers and one
receiver if designing for a DTE (one driver
and two receivers for a DCE).
A programmable transceiver such as the
SP332 is a convenient solution in a design
that requires extra single ended or differential
drivers/receivers. As shown in Figure 28, the
SP332 can be configured to four different
variations.
The SP332 in Figure 29 is configured for two
single-ended drivers and one diffferential
receiver. For a DTE design, the two drivers
are used for LL and RL signals and
the receiver is used for the TM signal. This
configuration was selected because the two
RS-232 drivers can be used for RS-423 by
connecting a zener clamping diode to ground
on the two driver outputs. The diodes will
limit the voltage swing on the outputs so that
the V_OC = ±4V to ±6V adheres to the RS-423
specification. The differential receiver can
be easily configured to RS-423 by ground-
ing the non-inverting input. The receiver will
adhere to the RS-423 specifications.
CIRCUIT
CIRCUIT NAME
MNEMONIC
SG
SC
RC
IS
IC
TR
DM
SD
RD
TT
ST
RT
RS
CS
RR
SQ
NS
SF
SR
SI
SSD
SRD
SRS
SCS
SRR
LL
RL
TM
SS
SB
SIGNAL GROUND
SEND COMMON
RECEIVE COMMON
TERMINAL IN SERVICE
INCOMING CALL
TERMINAL READY
DATA MODE
SEND DATA
RECEIVE DATA
TERMINAL TIMING
SEND TIMING
RECEIVE TIMING
REQUEST TO SEND
CLEAR TO SEND
RECEIVER READY
SIGNAL QUALITY
NEW SIGNAL
SELECT FREQUENCY
SIGNAL RATE SELECTOR
SIGNAL RATE INDICATOR
SECONDARY SEND DATA
SECONDARY RD
SECONDARY RS
SECONDARY CS
SECONDARY RR
LOCAL LOOPBACK
REMOTE LOOPBACK
TEST MODE
SELECT STANDBY
STANDBY INDICATOR
CIRCUIT
CIRCUIT
DIRECTION
TYPE
--------------
TO DCE COMMON
FROM DCE
TO DCE
FROM DCE
TO DCE
CONTROL
FROM DCE
TO DCE
FROM DCE
DATA
TO DCE
FROM DCE _TIMING
FROM DCE
TO DCE
FROM DCE
FROM DCE
FROM DCE ^CONTROL
TO DCE
TO DCE
TO DCE
FROM DCE
TO DCE
DATA
FROM DCE
TO DCE _CONTROL
FROM DCE
FROM DCE
TO DCE
TO DCE _CONTROL
FROM DCE
TO DCE
FROM DCE
CONTROL
1 _{RS-449 Interchange Circuits Table}
SEL A
0
0 1 1
SEL B
0 1
0 1
LOOPBACK 1 1 1 1
SHUTDOWN
0
0
0
0
Figure 28. Mode selection for the SP332
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
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