SP503CF datasheet(12/29 Pages) SIPEX

12 / 29 page

Date: 7/29/04

SP503 Multiprotocol Transceiver

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

Ω, 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

15k

Ω 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

100

Ω. In order to meet the V.35 input imped-

ance of 100

Ω, 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

Mode:

RS-232

V.35

RS-422

RS-485

RS-449

EIA-530

RDEC

3–RDEC0

0000

0010

1110

0100

0101

1100

1101

RD(a)

Undefined

RS-232

V.35–

RS-422–

RS-485–

RS-422–

RD(b)

Undefined

15kΩ to GND

V.35+

RS-422+

RS-485+

RS-422+

RT(a)

Undefined

RS-232

V.35–

RS-422–

RS-485–

RS-422–

RT(b)

Undefined

15kΩ to GND

V.35+

RS-422+

RS-485+

RS-422+

CS(a)

Undefined

RS-232

RS-422–

RS-485–

RS-422–

CS(b)

Undefined

15kΩ to GND

15KΩ to GND

RS-422+

RS-485+

RS-422+

DM(a)

Undefined

RS-232

RS-422–

RS-485–

RS-422–

DM(b)

Undefined

15kΩ to GND

15KΩ to GND

RS-422+

RS-485+

RS-422+

RR(a)

Undefined

RS-232

RS-422–

RS-485–

RS-422–

RR(b)

Undefined

15kΩ to GND

15KΩ to GND

RS-422+

RS-485+

RS-422+

IC(a)

Undefined

RS-232

RS-422–

RS-485–

RS-423

IC(b)

Undefined

15kΩ to GND

15KΩ to GND

RS-422+

RS-485+

15KΩ to GND

SCT(a)

Undefined

RS-232

V.35–

RS-422–

RS-485–

RS-422–

SCT(b)

Undefined

15kΩ to GND

V.35+

RS-422+

RS-485+

RS-422+

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 100k

Ω 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 5k

Ω is internally con-

nected, which will ensure a logic high output.

Table 2. SP503 Receivers

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