%
5. BeforeclosingtheRS-422 circuit at theendof communication,sendthe End
Polling command to the communicating PT to report that communication is
ended.
Host computer program
RS-422 circuit
PT operation
OPEN command
PRINT # command
LINE INPUT # command
CLOSE command
Open circuit
Send instruction
Close circuit
Send instruction
Receive instruction
Send instruction
PRINT # command
PRINT # command
PRINT # command
PRINT # command
Start polling
End polling
Receive instruction
Receive instruction
Unit # 1
Receive instruction
Receive instruction
Unit # 15
End polling
Start polling
Open
status
After a circuit has been opened, it can be used until it is closed again.
Refer to
4-1 RS-232C Interface Unit Communications
for details about the com-
mands.
4-2-2 Polling Procedure
To communicate with the RS-422 Interface Unit, the communication circuit is
opened before the polling commands are used.
If a touch switch is pressed or the screen changed on a non-polled PT, the host
computer is not notified until start of communication is indicated with the Start
Polling command.
The polling command must be used before commencing communication even
when only a single PT is connected to the host computer.
Whena PT is polled after a long time,the notify datastored up to thattime is sent
continuously.
Start Polling Command
This command notifies the PT with the specified terminal number that commu-
nication has started. Refer to
3-2-2 RS-422 Interface Unit Terminal Number
for
details about setting the terminal number.
Format
n
1
,n
2
: terminal number 00 to 15 (2-digit decimal)
1B
[ESC]
40
@
n
1
n
2
Example
PRINT #1,CHR$ (&H1B);”@05”
End Polling Command
This command notifies the the communicating PT that communication has en-
ded. To switch PTs during communication, first send the End Polling command
to the communicating PT before sending the Start Polling command to the next
PT.
Format
1B
[ESC]
41
A
Section 4-2
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