Chapter 11 Communication Specifications

11.5 Modem Control Function

The 14-point or higher MICRO-EH is equipped with a modem control function. The modem control function can be operated using task codes. To use this function, it is necessary to set No.2 of the DIP SW.

For details on the communication specifications, see Table 11.1, “Specifications of port 1.” * The 10-point type CPU does not have this function.

Connecting two operating modems may be difficult if there is a significant difference between them in terms of communication speeds. Thus, use the models having the same communication speed.

11.5.1 Configuration

Personal

 

 

Modem

 

Modem

 

 

 

MICRO-EH

computer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RS-232C

 

 

 

 

 

 

 

 

(MAX 57.6 kbps)

 

 

 

 

 

 

Public line

 

 

 

 

 

 

 

 

Figure 11.5 Modem connection configuration diagram

 

 

 

Table 11.7 List of port 1 signals when a modem is connected

Pin No.

 

Signal

 

 

Direction

 

 

 

Meaning

 

abbreviation

 

CPU

Host

 

 

 

 

 

 

 

 

 

1]

 

 

SG1

 

 

 

 

Signal ground

2]

 

CD1

 

 

 

 

Carrier receive in-progress notification signal

 

 

 

 

 

 

 

 

 

Connected to CD in the modem.

3]

 

 

ER1

 

 

 

 

Communication enabled signal of the terminal

4]

 

 

ER2

 

 

 

 

Not used

5]

 

 

SD1

 

 

 

 

Data sent by the CPU

 

 

 

 

 

 

 

 

 

Connected to SD in the modem.

6]

 

RD1

 

 

 

 

Data received by the CPU

 

 

 

 

 

 

 

 

 

Connected to RD in the modem.

7]

 

DR1

 

 

 

 

Communication enabled signal of the modem

 

 

 

 

 

 

 

 

 

Connected to DR in the modem.

8]

 

 

RS1

 

 

 

 

Transmission request signal

 

 

 

 

 

 

 

 

 

Connected to RS in the modem.

11.5.2 AT Commands

The AT commands are used to make various modem settings, and are set from the host computer. The MICRO-EH issues the AT commands automatically for initial setting. Other than this, the AT commands are not used.

Refer to instruction manual or other documents furnished by modem manufacturers for details on the AT commands. In AT commands, an instruction sent to the modem from the host is called a “command,” and the character string in response to the “command” returned to the host from the modem is called a “result code.”

AT commands always begin with the character string “AT,” and a return code is input at the end of the command. However, A/ is excluded. The command that follows the “AT” can have multiple inputs in a single line.

Example)

A

T

&C

1

&S

0

P

2

CR

LF

AT commands

 

CD signals: Follows the

DR signals: Always On

20 pps (pulse setting)

 

 

 

 

carrier signals generated

 

 

 

 

 

 

 

 

by the opposite device

 

 

 

 

 

 

(1)Format

1] AT command format

A

T

command parameter command parameter · · · ·

2]

Result code format

 

 

 

 

 

 

 

CR

LF

Result code (word)

 

 

CR

LF

 

Result code (number)

 

CR

 

LF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CR

LF

11-5

Page 258
Image 258
Hitachi NJI-350B manual Modem Control Function, Configuration, AT Commands