13-4
Communication
13
13-3 Communication format
The communication formats of the commands and responses between the IV-S20 and a personal
computer are outlined below.
*1 Processing code and text
- They depend on the contents of communication. (See pages 13-1 and 13-6 and after.)
- On abnormal termination, no text is provided.
*2 Termination code
The termination code is a 2-digit hexadecimal number.
- When an output is sent through the general purpose serial I/F, 00
(H)
is sent on normal termi-
nation.
- On abnormal termination, a code other than 00
(H)
is sent. (See page 15-3.)
*3 Checksum code (SC
H
and SC
L
)
To improve the reliability of the transmitted data, in addition to a parity check, error detection
by a checksum is used for error detection.
When the IV-S20 does not need to complete a checksum for error detection, use an @ (at
sign: ASCII code 40
(H)
) in each of the checksum codes SC
H
and SC
L
included in the command.
[Error detection using a checksum]
The ASCII code for each data byte, from the processing code to the end of text (prior to the
checksum code), is added. The final value is compared to the checksum code which is
treated the same way. If the two values are identical, the command is considered to be
valid. I/F they are not identical, an error has occurred during transmission.
Header
:
* *
* * .............. * *
Header
SC
H
CR
SC
L
RC
H
RC
L
Text
Termination
code
Terminator
Processing
code
Checksum code
Value increment range for
checksum
SC
H
SC
L
CR
Checksum code
Terminator
Text
Processing
code
:
* * * * ............... * *
Value increment range for
checksum
Ë
Command
Ë
Response
Ë
Command
Ë
Response
:
* * * *
...............
* *
Header
SC
H
SC
L
CR
Checksum code
Terminator
Text
:
* * * *
* *
Header
SC
L
RC
H
RC
L
Text
*3
*1
Processing
code
*1
Termination
code
*1
*2
Terminator
*1
Processing
code
*3
Checksum code
SC
H
CR
...............