3. POSITIONING SIGNALS
3 − 48
3.3 Special Relays (SP.M)
The servo system CPU has 256 special relay points from M9000 to M9255.
Of there, the 7 points from M9073 to M9079 are used for positioning control, and
their applications are indicated in Table 3.2.
Table 3.2 Special Relays
Device No. Signal Name Signal Direction Refresh Cycle Fetch Cycle
M9073 PCPU WDT error flag
M9074 PCPU REDAY-completed flag
M9075 In-test-mode flag
M9076 External emergency stop input flag
M9077 Manual pulse generator axis setting error flag
M9078 Test mode request error flag
M9079 Servo program setting error flag
PCPU → SCPU END
(1) WDT error flag (M9073)...................................Signal sent from PCPU to SCPU
This flag comes ON when a "watchdog timer error" is detected by the PCPU's
self-diagnosis function.
When the PCPU detects a WDT error, it executes an immediate stop without
deceleration on the driven axis.
When the WDT error flag has come ON, reset the servo system CPU with the
key switch.
If M9073 remains ON after resetting, there is a fault at the PCPU side.
The error cause is stored in the PCPU error cause storage area (D9184) (see
Section 3.5.2).
(2) PCPU REDAY-completed flag (M9074)...........Signal sent from PCPU to SCPU
This flag is used to determine whether the PCPU is normal or abnormal from
the sequence program.
(a) When the PLC READY flag (M2000) turns from OFF to ON, the fixed
parameters, servo parameters, limit switch output data, etc., are checked,
and if no error is detected the PCPU READY-completed flag comes ON.
The servo parameters are written to the servo amplifiers and the M-codes
are cleared.
(b) When the PLC READY flag (M2000) goes off, the PCPU READY-completed
flag also goes OFF
PLC READY
(M2000)
PCPU READY
completed flag
(M9074)
Writing of servo parameters to
servo amplifiers
Clearance of M-codes
t
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