mc1451a-e ETC-unknow, mc1451a-e Datasheet - Page 25

• Manufacturer Part Number: mc1451a-e
• Description: Advanced Brushless Motor Control Chipset
• Manufacturer: ETC-unknow

After a breakpoint condition has been satisfied it is no longer
active. To set up another breakpoint condition, a new one must be
explicitly set by the host.
The double-buffered registers that are shifted to the active
registers do not change upon being shifted, only the active
registers change.
Except for the MULTI_AXIS command, parameter loading and updating
is controlled individually for each axis. In addition each axis has a
separate 32-bit breakpoint register, and can be set to various individual
breakpoint conditions.
External Breakpoints and Homing
By connecting a home input sensor to the home signal input of the
MC1231-series chipsets it is possible to cause the chipset to halt a
motion at the moment it receives the home signal. This capability
makes it ideal for performing a home sequence. The following host I/O
sequence illustrates this:
GET_HOME
SET_CAPT_HOME
CLR_STATUS
GET_CAPT
SET_POS 12345
SET_VEL 23456
SET_ACC 345
UPDATE
SET_EXT_BRK
SMOOTH_STOP
This sequence will start a homing move which will come to a smooth
stop as soon as the axis encounters the home switch. In addition the
capture register will be loaded with the exact location of the home
sensor. This register can be used in conjunction with the
GET_ACTL_POS and SET_ACTL_POS commands to set the position
to any desired location. For example if it is desired that the home
sensor be located at a position of 0, then the new position should be set
to the current actual axis position minus the capture position. This is
shown in the sequence below, which should be executed after the axis
has come to a stop.
current_pos = GET_ACTL_POS
capture_pos = GET_CAPT
SET_ACTL_POS (current _pos - capture_pos)
As is the case for all of the breakpoint modes, the external breakpoint
can not only be used to stop an ongoing move, but to start or otherwise
modify a move as well. This flexibility makes it well suited for
applications such as cut-on-the-fly or other externally-initiated motions.
; check to make sure axis not already at
; home. If so, then a 'reverse' move must
; be made to retract axis from home switch.
; This 'reverse' sequence is not indicated
; here for simplicity sake
; set trigger capture to home signal
; clear status register
; clear out any previous captures
; load home move parameters
; start home move
; initiate external breakpoint mode
; load (but do not update) a stop command
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Disabling Automatic Profile Update
Normally, when a breakpoint condition has been satisfied, it causes the
profile & filter parameters to be automatically updated. For certain types
of profiles however, it may be desirable to still use the breakpoint
mechanism (to allow it to generate a host interrupt for example), but not
to have the profile update.
Whether the profiles are automatically updated or not for a given axis is
controlled by the commands SET_AUTO_UPDATE_ON and
SET_AUTO_UPDATE_OFF. When auto update is set to on, the
breakpoint/profile mechanism behaves as described above. When set
to off, upon a breakpoint condition, no profile update will occur. When in
this mode the only way to update the profile is to use the UPDATE
command or the MULTI_UPDATE command.
Travel Limit Switches
The MC1231-series chipsets support motion travel limit switches that
can be used to automatically recognize an "end of travel" condition.
The following figure shows a schematic representation of an axis with
travel-limit switches installed, indicating the "legal" motion area and the
over-travel regions.
There are two primary services that the MC1231A provides in
connection with the over-travel limit switch inputs:
To recover from an over-travel condition the corresponding status bits
in the status word should be reset (see the section of this manual on
axis status for details on resetting status word bits). Once this has been
performed the host can command a trajectory move to bring the axis
out of the over-travel region.
The over-travel detector is 're-armed' when the axis exits the over travel
condition.
Only one over-travel signal can be processed at a time. For
example if the negative over travel switch becomes active, the
corresponding status bits must be cleared, and the axis moved
1)
2)
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over-travel
negative
region
The host can be automatically notified that an axis has entered
an over-travel condition, allowing the host to take appropriate
special action to manage the over-travel condition.
Upon entering an over-travel condition, the trajectory generator
will automatically be halted, so that the motor does not travel
further into the over travel region.
negative limit
switch
Legal travel region
positive limit
switch
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over-travel
positive
region