6.6 Latch Function
6-13
6
Function/Command Related Parameter
s
6.6
Latch Function
Three types of current position latch function using an external signal input are available:
•
Latching by using the move command with the latch function (EX_FEED, EX_POSING, ZRET)
•
Latching based on the latch request set by the LT_REQ1 and LT_REQ2 bits
•
Continuous latch based on the latch request set by the LT_REQ2 bit
An overview of the latch operation is presented below.
*
The specification differs from that of the MECHATROLINK-II compatible profile. Monitor the latched position by
selecting the latched position with monitor selection bits SEL_MON1 to 3.
The relationship among the signals related to latching is shown in the diagram below.
Even if a request for latching is made, latch signals will not be accepted until the latching con-
ditions are satisfied.
Whether the latching conditions have been satisfied or not can be checked at LT_RDY1 and
LT_RDY2 selected with common monitor 1 (CMN1) and common monitor 2 (CMN2). These
monitors correspond to the 0th and 1st bits of the SV_STAT field of common parameter 89
(PnB12).
In either of the following cases, latching will not be performed since the latching conditions are
not satisfied.
•
Outside the latching allowable area set by parameters
•
Inside the latching disabled area in the operation sequence for the ZRET command
Operation when Latching is Completed
Type
Operation
Move Command with Latch
Function
Latching Based on the
Latch Request Set by the
LT_REQ1 and LT_REQ2
Bits
Continuous Latch Based on
the Latch Request Set by
the LT_REQ2 Bit
Latch Opera-
tion
The slave station starts latch-
ing on reception of the com-
mand if LT_REQ1 = 1, and
ends latching on input of the
specified latch signal.
The slave station starts
latching if LT_REQ1 = 1 and
LT_REQ2 = 1, and ends
latching on input of the
specified latch signal.
The slave station starts
latching if LT_REQ2 = 1, and
repeats latching on input of
the specified latch signal.
Canceling
Latching
Cancelled by LT_REQ1 = 0
Cancelled when the slave sta-
tion receives another com-
mand
Cancelled by LT_REQ1 = 0
and LT_REQ2 = 0
Cancelled by LT_REQ2 = 0
Checking
Completion of
Latching
Check L_CMP1.
Check L_CMP1 and L_C-
MP2.
Check L_CMP2 and
EX_STATUS.
Outputting
Latched
Position
*
LPOS1
LPOS1, 2
LPOS2
Latching
Allowable Area
According to the settings of Pn820 and Pn822
OFF
ON
LT_REQ
LT_RDY
L_CMP
OFF
ON
OFF
ON
OFF
ON
Latch condition not e
s
tabli
s
hed
Latch
s
ignal