Colorado Electronic Product Design - Analog / Digital Design, Telecommunications, DSP, Embedded Systems

 

EIA232

 

EIA232 is a standard way for serial binary communication between data terminal equipment (DTE) and data circuit terminal equipment (DCTE). The EIA232 signal are unbalanced (Single Ended), unidirectional (point-to-point) reference to ground. Normal output ranges are ±5 volts. Data is transfer in an asynchronous frame format in 8-bit binary packets. This protocol allows the system to recover quickly from errors. The EIA 232 standard is rated to operate at 20kbps. The Pin out of the DB25, DE9, and RJ45 table are as follows:

DB25 Pin Number

Direction

Pin assignment

1

-

Protective Ground

2

Out

Transmit data (Tx)

3

In

Receive data (Rx)

4

Out

Request to send (RTS)

5

In

Clear to send (CTS)

6

In

Data set ready (DSR)

7

-

Signal ground (SGND)

8

In

Data carrier detect (DCD)

9

-

Test pin

10

-

Test pin

11

-

Unassigned

12

In

Data carrier detect (CH2 only)(SDCD)

13

In

Clear to send (CH2 only)(SCTS)

14

Out

Transmit data (CH2 only)(STD)

15

Out

Transmitter clock (TCLK)(DB)

16

In

Receive data(SRD)

17

In

Receive clock (RCLK)(DD)

18

-

Local Loopback (LL)

19

Out

Request to send (CH2 only)(SRTS)

20

Out

Data terminal ready (DTR)

21

-

Signal quality detector(RL/SQ)

22

In

Ring indicator(RI)

23

Out

Data signal rate detector (CH/CI)

24

-

Auxiliary clock (CH2 only)(DA) (XCLK)

25

-

-

Table 1: EIA232 serial connector pin out for a DB25
DB25

Figure 1 : DB25 Pin out numbering

 

DE9 Pin Number

Direction

Pin assignment

1

In

Data carrier detect (DCD)

2

In

Receive data (Rx)

3

Out

Transmit data (Tx)

4

Out

Data terminal ready (DTR)

5

-

Signal ground

6

In

Data set ready (DSR)

7

Out

Request to send (RTS)

8

In

Clear to send (CTS)

9

In

Ring indicator(RI)


Table2: EIA232 serial connector pin out for a DE9

DE9
Figure 2: DE9 Pin out numbering

 

DE9 Pin Number

DB25 Pin Number

Pin assignment

1

8

Data carrier detect (DCD)

2

3

Receive data (Rx)

3

2

Transmit data (Tx)

4

20

Data terminal ready (DTR)

5

7

Signal ground

6

6

Data set ready (DSR)

7

4

Request to send (RTS)

8

5

Clear to send (CTS)

9

22

Ring indicator(RI)

  Table 3: DE9 to Db25 converter pin out

Convert
Figure 3 : DB25 to DE9 conversion

RJ-45 Pin Number

Direction

Pin assignment

1

In

Ring Indicator (RI)

2

In

Data carrier detect (DCD)

3

Out

Data terminal ready (DTR)

4

-

Signal Ground / Common

5

In

Receive data (Rx)

6

Out

Transmit data (Tx)

7

In

Clear to send (CTS)

8

Out

Request to send (RTS)


 
Table 4: EIA232 serial connector pin out for a RJ-45

 

RJ-45

Figure 4 : RJ-45 Pin out

The Null modem is a communication method devised to allow two DTE systems to connect directly. This is accomplished by cross linking the transmit and receive lines. An example for a DE9 is in figure 5.

 

Connector 1

Connector 2

2

3

3

2

5

5


Table 5: DE9 Null modem

Null
Figure 5 : DE9 Null Modem connection


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