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11. TROUBLESHOOTING
MELSEC-A
11.
TROUBLESHOOTING
This chapter describes errors which can occur with the AJ71C24 proce-
dures.
11.1 NAK Error Codes with Dedicated Protocols
Table 11.1 gives the error codes and their descriptions when the NAK code
is transmitted between the computer and the PC CPU as 2-digit ASCII
(hexadecimal) between OOH and FFH.
If several errors occur simultaneously, the codewith the lowest numbertakes
precedence and is transmitted.
If any of the following errors occur, the transmission seauences are initial-
izedand LEDs 2 - ~ 3 ~ a n d
4-NEU (LED Nos. 4 and
7)
are'turned ON
Table 11.1 Error Code List
OOH
Error
Disable
during
RUN
Parity
error
Sum
check
error
Protocol
error
Framing
error
Overrun
error
>haracter
nrea error
-
Error Description
Invalid access has been made during RUN.
(1) Data has been written to a PC CPU with
the SW22 OFF (write disable during RUN).
(2) Sequence program and parameters have
been written.
Parity error
With the SW16 ON (parify enabled), the
party cneck result does not match the
slate of SW17 loddlcvcn oaritvl.
.
,,
Sum check error
With the SW21 ON (sum check enabled),
the sum check result of received data
does not match the sum check code of
transmitted data, i.e., send data is dif-
ferent from received data.
~
-
Communications protocol not valid.
Communications have been made with a
protocol different from the one set by the
mode setting switch.
Framing error
Data does not match the setting of SW18
(stop bit).
Overrun error
New data has been transmitted before
AJ71 C24 receives all the preceding data.
Character area A, 8 , or C error, or designated
command does not exist.
(1) The designation of the character area A,
8,
or C for the control protocol set with the
mode setting switch is not correct.
(2) A command used with the protocol does
not exist.
(For example,
a
subsequence program was
designated to be used with A1N or A2NCPU.)
The set device number does not exist in the
set PC CPU.
(3) The device number is not
set
with the re-
quired number of characters.
(ACPU common command: 5 characters,
AnACPU dedicated command: 7 characters)
-
Indicator
LED No.
2-CIN
(LED No.16)
4 C I N
(LED No.20)
2-PIS
(LED No.17)
4-PIS
(LEO No.21)
2-PIS
(LED No.17)
4-PIS
(LED No.21)
2-PRO
(LED No.18)
4-PRO
(LED No.22)
2-sio
(LED No.19)
4-SIO
(LED No.23)
2-510
(LED No.19)
4510
(LED No.23)
2-PRO
(LED No.18)
4-PRO
(LED No.22)
Corrective Actions
(1) Start communicationss
after turning ON SW22.
(2) Write parameters after set-
ting the PC CPU to STOP.
Check control protocol,
change the SW setting
01
data.
Check data transmitted from
computer and sum check
result. Correct invalid data.
Check and correct the mode
setting switch position and
control protocol and restart
data communications.
Change the setting of SW18
or the control protocol.
Decrease the data transmis-
sion speed and restart data
communications.
(1) Check and correct the char-
acter area A,B, or C and
restart data communica-
tions.
(2) See the functions list in
Section 3.3.1 and the
ACPU User's Manual to cor-
rect the designated com-
mands, and restart data
communications.
(3) See Section 8.7.1 to cor-
rect the number of setting
characters of the device
number, and restart data
communications.
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