Modem Control Function - Hitachi HIDIC MICRO-EH Applications Manual

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
computer
Pin No.
abbreviation
1]
2]
3]
4]
5]
6]
7]
8]
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
AT commands
(1) Format
1] AT command format
A
2] Result code format
CR
Result code (number)
Modem
Public line
Figure 11.5 Modem connection configuration diagram
Table 11.7 List of port 1 signals when a modem is connected
Signal Direction
CPU
SG1
CD1
ER1
ER2
SD1
RD1
DR1
RS1
&C 1
CD signals: Follows the
carrier signals generated
by the opposite device
command parameter command parameter · · · ·
T
LF Result code (word)
CR LF
Chapter 11 Communication Specifications
Modem
MICRO-EH
RS-232C
(MAX 57.6 kbps)
Host
Signal ground
Carrier receive in-progress notification signal
Connected to CD in the modem.
Communication enabled signal of the terminal
Not used
Data sent by the CPU
Connected to SD in the modem.
Data received by the CPU
Connected to RD in the modem.
Communication enabled signal of the modem
Connected to DR in the modem.
Transmission request signal
Connected to RS in the modem.
&S 0 P
20 pps (pulse setting)
DR signals: Always On
CR LF
11-5
Meaning
2 CR LF
CR LF