Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
354
Synchronizing Turbo PMAC to External Events
Motion program
The motion program freezes the time base and calculates the first move. But actual execution of this
move will not happen until the time base has been triggered.
The motion program freezes the time base and calculates the first move. But actual execution of this
move will not happen until the time base has been triggered.
CLOSE
OPEN PROG 12 CLEAR
I5193=$350A
I5193=$350A
; Time base source address is triggered time-base conversion in table
; (2nd line)
DWELL0
; Stop lookahead in program
M199=$9
; Freeze time-base
LINEAR
; Linear move mode
INC
; Incremental move specification
TA10
; 36 degrees of master is 10 msec
TS0
; No S-curve
DELAY12.5
; 45 degrees of master is 12.5 msec
TM50
; 36+144 deg of master is 50 msec
A360
; One full revolution of slave axis
CLOSE
PLC Program
The PLC program simply looks to see if the time base has been frozen; if so, it arms the time base. In the
armed state, the triggered time-base conversion table entry looks for the trigger every servo cycle.
The PLC program simply looks to see if the time base has been frozen; if so, it arms the time base. In the
armed state, the triggered time-base conversion table entry looks for the trigger every servo cycle.
CLOSE
OPEN PLC 10 CLEAR
IF (M199=$9)
IF (M199=$9)
; Has time-base been frozen?
M199=$B
; Then arm for trigger
ENDIF
CLOSE
Synchronizing Turbo PMAC to other Turbo PMACs
When multiple Turbo PMACs are used together, inter-card synchronization is maintained by passing the
servo clock signal from the first card to the others. With careful writing of programs, this permits
complete coordination of axes on different cards.
servo clock signal from the first card to the others. With careful writing of programs, this permits
complete coordination of axes on different cards.
Turbo PMAC provides the capability for putting multiple cards together in a single application. To get
the cards working together properly in a coordinated fashion, several factors must be considered:
the cards working together properly in a coordinated fashion, several factors must be considered:
•
Host communications addressing
•
Clock timing
•
Motion program timing
The host communications addressing is covered in Talking to Turbo PMAC and Writing a Host
Communications Program sections of this manual. The timing (synchronization) issues are covered below.
Communications Program sections of this manual. The timing (synchronization) issues are covered below.
Clock Timing
Turbo PMAC cards use a crystal clock oscillator (the master clock) as the fundamental time measuring
device. Each Turbo PMAC has its own crystal oscillator. Although these crystals are made to a very
tight tolerance (50 ppm accuracy standard; 10 ppm with Option 8) they are not exactly the same from card
to card. The phase and servo clock signals that actually control the timing of moves are derived from the
crystal clock frequency, and so have the same tolerance. This can cause cards to lose synchronicity with
each other over long move sequences if they are each using their own master clock. Generally, this will
be noticeable only if a continuous move sequence lasts more than 10 minutes. For example, in the worst
case, with 100 ppm difference between two cards, at the end of a 10-minute continuous sequence, the
cards will be off by 60 msec.
device. Each Turbo PMAC has its own crystal oscillator. Although these crystals are made to a very
tight tolerance (50 ppm accuracy standard; 10 ppm with Option 8) they are not exactly the same from card
to card. The phase and servo clock signals that actually control the timing of moves are derived from the
crystal clock frequency, and so have the same tolerance. This can cause cards to lose synchronicity with
each other over long move sequences if they are each using their own master clock. Generally, this will
be noticeable only if a continuous move sequence lasts more than 10 minutes. For example, in the worst
case, with 100 ppm difference between two cards, at the end of a 10-minute continuous sequence, the
cards will be off by 60 msec.