Chapter 11 Communication Specifications

(2)1:n station communication on RS-485

When station number mode is used on RS-485, termination command (NAK FF) from host/PC can conflict with reply from CPU, and CPU can fail to receive this command. Pay attention to this possibility at using this command.

(3)Port 2 hardware

The circuit diagram of port 2 and the signal list are shown in Figure 11.4 and Table 11.6 respectively.

Micro processor

 

 

7]

SG

 

VCC

5]

VCC

 

 

 

RS2

 

14]

RSP

 

 

6]

RSN

CS2

 

15]

CSN

 

 

8]

CSP

TX2

 

13]

SDP

 

 

12]

SDN

RX2

 

10]

RDN

 

 

11]

RDP

 

 

9]

RT

8]

15] 7]

14] 6]

13] 5]

12]

11] 4]

10] 3]

9] 2]

1]

Figure 11.4 Circuit diagram and pin numbers for port 2

Table 11.6 List of port 2 signals

Pin No.

Signal

Direction

Meaning

 

abbreviation

CPU Host

 

1]

NC

 

Not used

2]

NC

 

Not used

3]

NC

 

Not used

4]

NC

 

Not used

5]

Vcc

 

5 V DC is supplied.

6]

RSN

 

Transmission request signal. When it is high low, CPU is ready to receive data..

7]

SG

 

Signal ground

8]

CSP

 

Receive enabled signal. When it is high, connected device is ready to receive data.

9]

RT

 

Terminating resistor (120Ω). Connect to pin 10 if necessary.

10]

RDN

 

Data received by the CPU -

11]

RDP

 

Data received by the CPU +

12]

SDN

 

Data sent by the CPU -

13]

SDP

 

Data sent by the CPU +

14]

RSP

 

Transmission request signal. When it is high level, CPU is ready to receive data.

15]

CSN

 

Receive enabled signal. When it is low, connected device is ready to receive data.

11.4 General purpose port (Port 1,2)

General purpose port can be configured either port 1 or port 2 by FUN 5 command in user program. General purpose port enables serial communication to devices like bar code reader by TRNS/RECV command in user program.

Even if configured, the port works as general purpose port only CPU is in RUN status. Port is changed back to dedicated port when CPU is in STOP status.

* General purpose port is supported by software version 1.30 (WRF051=H0130) or newer.

General purpose port

CPU in STOP

Dedicated port

Switching

CPU in RUN

automatically

 

General purpose port

 

 

11-4

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Hitachi NJI-350B manual General purpose port Port 1,2, 1n station communication on RS-485, Port 2 hardware, 11-4