SP502 datasheet(12/32 Pages) SIPEX

12 / 32 page

Rev. 7/21/03

SP502 Multi-Mode Serial Transceiver

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

RS-422+

RS-485+

RS-422+

DM(a)

Undefined

RS-232

RS-422–

RS-485–

RS-422–

DM(b)

Undefined

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

RS-422+

RS-485+

RS-422+

IC(a)

Undefined

RS-232

RS-422–

RS-485–

RS-423

IC(b)

Undefined

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 SP502 is equipped with seven (7) receivers

which can be programmed in six (6) different

modes of operation. One of the seven (7) receiv-

ers (RxT) is part of a half-duplex channel, which

means its inputs are shared with a driver

output, as shown in the Mode Diagrams. The

RxT receiver has its inputs internally connected

to the TT(a) and TT(b) pins. The select pin

labeled ST/TT enables either the TT-driver or

the ST-driver, but it does not disable the re-

ceiver. The RxT receiver is always connected to

the TT(a) and TT(b) pins. Any signal that is

received or transmitted on TT(a) and TT(b) will

trigger a TTL-output at the RxT pin.

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,

Table 2. SP502 Receivers

can operate up to 120kbps. The RS-232 drivers

are used in RS-232 mode for all signals, and also

in V.35 mode where they are used as the control

line signals.

The RS-423 drivers output a minimum of

±3.6V

level single–ended signals (with 450

Ω loading)

and can operate up to 120kbps. Open circuit

OL and VOH measurements may exceed the

±6V limitation of RS-423. The RS-423 drivers

are used in RS-449 and EIA-530 modes as RL

and LL outputs.

The third type of driver supports RS-485, which

is a differential signal that can maintain

±1.5V

differential output levels with a worst case load

of 54

Ω. The signal levels and drive capability of

the RS-485 drivers allow the drivers to also

support RS-422 requirements of

±2V differen-

tial output levels with 100

Ω loads. The RS-422

drivers are used in RS-449 and EIA-530 modes

as clock, data, and some control line signals.

The RS-485–type drivers are also used in the

V.35 mode. V.35 levels require

±0.55V signals

with a load of 100

Ω. In order to meet the voltage

requirements of V.35, external series resistors

with source impedance termination resistors

must be implemented to voltage divide the driver

outputs from 0 to +5V to 0 to +0.55V. Figure 6

shows the values of the resistor network and

how to connect them. The termination network

also achieves the 50

Ω to 150Ω source imped-

ance for V.35. For applications that require

V.11 signals for clock and data instead of V.35

levels, omit the external termination networks.

All of the differential drivers, RS-485, RS-422,

and V.35 can operate up to 5Mbps.

*TT(a) and TT(b) can be programmed as driver outputs or receiver inputs.

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