SP503 Datasheet, PDF (12/29 Pages) Sipex Corporation – Multiprotocol Transceiver

Receivers
The SP503 has seven (7) independent receivers
which can be programmed for six (6) different
interface modes. One of the seven (7) receivers
(SCT) has an active–high enable control, as
shown in the Mode Diagrams.
Control for the mode selection is done via a 4–
bit control word that is independent from the
driver control word. The coding for the drivers
and receivers is identical. Therefore, if the modes
for the drivers and receivers are supposed to be
identical in the application, the control lines can
be tied together.
Like the drivers, the receivers are pre-arranged
for the specific requirements of the interface. As
the operating mode of the receivers is changed,
the electrical characteristics will change to sup-
port the requirements of clock, data, and control
line receivers. Table 2 shows a summary of the
electrical characteristics of the receivers in the
different interface modes. Unused receiver in-
puts can be left floating without causing oscilla-
tion. To ensure a desired state of the receiver
output, a pull–up resistor of 100kΩ to +5V
should be connected to the inverting input for a
logic low, or the non–inverting input for a logic
high. For single-ended receivers, a pull–down
resistor to ground of 5kΩ is internally con-
nected, which will ensure a logic high output.
There are three basic types of receivers —
RS-232, RS-423, and RS-485. The RS-232
receiver is a single–ended input with a threshold
of 0.8V to 2.4V. The RS-232 receiver has an
operating voltage range of ±15V and can re-
ceive signals up to 120kbps. RS-232 receivers
are used in RS-232 mode for all signal types, and
in V.35 mode for control line signals.
The RS-423 receivers are also single–ended but
have an input threshold as low as ±200mV. The
input impedance is guaranteed to be greater than
4kΩ, with an operating voltage range of ±7V.
The RS-423 receivers can operate up to 120kbps.
RS-423 receivers are used for the IC signal in
RS-449 and EIA-530 modes, as shown in Table 2.
The third type of receiver supports RS-485,
which is a differential interface mode. The
RS-485 receiver has an input impedance of
15kΩ and a differential threshold of ±200mV.
Since the characteristics of an RS-422 receiver
are actually subsets of RS-485, the receivers for
RS-422 requirements are identical to the
RS-485 receivers. RS-422 receivers are used in
RS-449 and EIA-530 for receiving clock, data,
and some control line signals. The RS-485
receivers are also used for the V.35 mode. V.35
levels require the ±0.55V signals with a load of
100Ω. In order to meet the V.35 input imped-
ance of 100Ω, the external termination network
of Figure 6 must be applied. The threshold of the
V.35 receiver is ±200mV. The V.35 receivers
Pin Label
RDEC₃–RDEC₀
RD(a)
RD(b)
RT(a)
RT(b)
CS(a)
CS(b)
DM(a)
DM(b)
RR(a)
RR(b)
IC(a)
IC(b)
SCT(a)
SCT(b)
Mode:
0000
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Table 2. SP503 Receivers
RS-232
0010
RS-232
15kΩ to GND
RS-232
15kΩ to GND
RS-232
15kΩ to GND
RS-232
15kΩ to GND
RS-232
15kΩ to GND
RS-232
15kΩ to GND
RS-232
15kΩ to GND
V.35
1110
V.35–
V.35+
V.35–
V.35+
RS-232
15KΩ to GND
RS-232
15KΩ to GND
RS-232
15KΩ to GND
RS-232
15KΩ to GND
V.35–
V.35+
RS-422
0100
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-485
0101
RS-485–
RS-485+
RS-485–
RS-485+
RS-485–
RS-485+
RS-485–
RS-485+
RS-485–
RS-485+
RS-485–
RS-485+
RS-485–
RS-485+
RS-449
1100
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-423
15KΩ to GND
RS-422–
RS-422+
EIA-530
1101
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-422–
RS-422+
RS-423
15KΩ to GND
RS-422–
RS-422+
Date: 7/29/04
SP503 Multiprotocol Transceiver
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© Copyright 2004 Sipex Corporation