TOIM5232

www.vishay.com

Vishay Semiconductors

Rev. 1.3, 04-Jul-12

8

Document Number: 81749

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

TOIM4232 (TOIM5232) ENCODER - DECODER INTERFACE



PROGRAMMING AND DATA TRANSMISSION

Operation

and

programming

of

the

TOIM4232

and

TOIM5232 interface devices are described below. Figure 1

shows the basic circuit design with 3 blocks: the RS232 to

3 V logic level shifter, the encoder/decoder (endec) circuit

and the transceiver to build a dongle for RS232 IrDA

extension. U1 is the level shifter to convert the RS232 logic

levels to unipolar 3 V logic; U2 is the encoder/decoder

Interface (endec) converting the NRZ - RS232 logic to IrDA

RZI - logic. The transceiver U3 transmits and receives

IrDA-compliant optical signals.

Fig. 1 - Circuit Diagram of the Demo Board

CIRCUIT DESCRIPTION

This circuit demonstrates the operation of an SIR IrDA

transceiver module. The transceiver U3 (e.g., as shown the

TFDU4101 or TFDU4301 or any other) converts the digital

electrical input signal to an optical output signal to be

transmitted, receives the optical signal, and converts these

to electrical digital signals. While the IrDA physical layer

protocol transmits only the “0” represented by a pulse with

a “Return to Zero Inverted (RZI)” logic, the RS232 protocol

needs a “No Return to Zero (NRZ)” representation. This

decoding/encoding process is done by U2, an interface

circuit stretching the received pulses and shortening the

pulses to be transmitted according to the IrDA physical layer

conditions. U1 interfaces the RS232 logic bipolar levels to

the 3 V logic of the Endec U2. The board is connected by

CON9 to the RS232 port (of a computer or other equipment.

The basic IrDA transmission speed is 9600 bit/s. This is the

default state of the Endec in power-on condition. Also,

activating the reset line at pin 1 (18) will set the device to this

basic state.



Note: The first pin number refers to TOIM4232; the second

number in brackets refers to TOIM5232. The crystal Y1

controls the timing of the Endec as a clock reference. The

outputs S1 and S2 are programmable outputs for control

operations and the outputs RD_LED and TD_LED can drive

LEDs for indicating data flow.

PROGRAMMING THE ENDEC

For decoding data rates other than the default, the endec is

to be programmed to set the internal counters and timers.

To switch the endec from the data transfer mode to the bit

rate programming mode, the input BR/D, pin 2 (19) is set

active high (BR/D = “1”). In this case the TOIM5232

interprets the 7 LSBs at the TD_232 input as a control word.

The operating bit rate will change to its supposedly new rate

when the BR/D returns back to low (“0”). Set the UART to 8

bit, no parity,

1 stop bit.



The control byte consists of 8 bit after the start bit (STA,

which is “0”). Keep in mind that the order is LSB first, MSB

last.



The diagram in figure 2 shows the programming byte

“0-1010-1100” in the order STA, B0, B1, B2, B3, S0, S1, S2,

X. This order is from right to left in table 1. B0 is sent first

as LSB (see figure 2).



The four least significant bits are responsible for the data

rate according to table 2 while the four higher bits are for

setting the IrDA pulse duration (S0), and the two outputs of

the endec S1 and S2. Bit 8 is not used.

RXD

TXD

RTS (BR/D)

U3

TFDU4101

2

4

6

8

5

3

1

7

Cathode

RXD

Vcc1

GND

SD

TXD

Anode

.

C3

J1

CON9

1

2

3

4

5

6

7

8

9

C6

C5

U2

TOIM4232

1(18)

2(19)

3(1)

4(2)

5(3)

6(4)

7(5)

8(7)

9(9)

15(16)

14(14)

13(13)

12(12)

11 *)

10(10)

16(17)

RESET

BR/D

RD_232

TD_232

Vcc_SD

X1

X2

GND

TD_LED

RD_IR

TD_IR

S2

S1

NC

RD_LED

Vcc

C7

U1

MAX3232

13

8

11

10

1

3

4

5

2

6

12

9

14

7

16

15

R1IN

R2IN

T1IN

T2IN

C+

C2+

V+

R1OUT

R2OUT

T1OUT

T2OUT

GND

C8

C9

R2

Z2

R1

+

C2

C1

Y1

J2

CON2

1

2

R4

C4

R3

C11

+

C10

External input

3.6V max.

DTR (RESET)

+

+

(TOIM5232)

TFDU4301

optional

TFDU4300:Vlog

TFDU4101:NC

This line not used fot TFDU4101

IRED

IRED

+

+

+

Vcc

*) (6), (8), (11), (15), (20)

21046