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MELSEC-Q
6 PROGRAMMING
(4) Checking cables for faults
The cable condition can be checked not only in the network diagnostics of GX
Developer but also with link special relays (SB) and link special registers (SW).
(Refer to Section 8.1.4.)
1) When a communication error occurs due to a cable fault, the error
count is stored in any of the link special registers (SW) in the table
below.
2) Turning ON Clear retry count (SB0005) will clear Number of retries
(SW00C8 and SW00C9).
Turning ON Clear communication error count (SB0006) will clear
Communication errors (SW00B8 to SW00C7).
Turning ON Clear forward loop transmission errors (SB0007) will clear
Line error on the forward loop side (SW00CC).
Turning ON Clear reverse loop transmission errors (SB0008) will clear
Line error on the reverse loop side (SW00CD).
No. Description No. Description
SB0005 Clear retry count
—
SB0006 Clear communication error count
SB0007 Clear forward loop transmission errors
SB0008 Clear reverse loop transmission errors
—
SW00B8
UNDER on the forward loop side/coaxial bus
UNDER
SW00B9
CRC on the forward loop side/coaxial bus
CRC
SW00BA
OVER on the forward loop side/coaxial bus
OVER
SW00BB
Short frame on the forward loop side/coaxial
bus short frame
SW00BC
Abort on the forward loop side (AB, IF)/coaxial
bus abort (AB. IF)
SW00BD
Timeout on the forward loop side (TIME)/
coaxial bus timeout (TIME)
SW00BE
Receiving 2k bytes or more on forward loop
side (DATA)/coaxial bus receiving 2k bytes or
more (DATA)
SW00BF
DPLL error on the forward loop side/coaxial
bus DPLL error
SW00C0 UNDER on the reverse loop side
SW00C1 CRC on the reverse loop side
SW00C2 OVER on the reverse loop side
SW00C3 Short frame on the reverse loop side
SW00C4 Abort on the reverse side (AB, IF)
SW00C5 Timeout on the reverse loop side (TIME)
SW00C6
Receiving 2k bytes or more on reverse loop
side (DATA)
SW00C7 DPLL error on reverse loop side
SW00C8
Number of retries on the forward loop side/
coaxial bus retries error
SW00C9 Number of retries on the reverse loop side
SW00CC Line error on the forward loop side
SW00CD Line error on the reverse loop side