6 Interface Between CNC And PLC
6 - 9
6.2 PLC Command Signal C-Bits
A C-bit is a command signal from the PLC to the HUST controller for CNC
functional control. The C-bits for HUST H2N controller are shown in Table 6-2 and
their meanings are discussed in the followings.
• Machine Lock/FEED-HOLD (C000)
C000 = 1 (high), All machine tool operation stops.
C000 = 0 (low), Machine tool operation in process.
If bit C000 is set high (1), control unit will stop all CNC operations. It will remain
stopped until C000 becomes low again. The relationship between C000 and the
machine motion is shown as below.
Fig 6-2 Relationship between C000 Signal and Machine
Effect of FEED-HOLD on output control command “G11 Pxxx Lyyy”
G11 Pxxx Lyyy, where xxx = the output number, yyy = 0 or any number.
1. If “yyy”=0 or void, this command is to turn ON the output specified by “xxx”
which can be turned OFF either by RESET or by G11 P-xxx. FEED-HOLD will
not change the status of output “xxx”.
2. If “yyy”= any number, this is to turn ON output “xxx” which can be turned OFF
by Feed-Hold. It will remain OFF as long as Feed-Hold is on. When Feed-Hold
is released, output “xxx” will be back ON. Use RESET or G11 P-xxx to turn
output “xxx” OFF.
C000 = 0
C000 = 1
C000 = 0
Machine in Motion
Motion Resumed
Machine Lock On
Motion Sto
ed
C000=1
Output
FEED-HOLD
“RESET” or
“G11 P-xxx”
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