PXD20RM Datasheet, PDF (1465/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

It should be kept in mind that the recommended way of operation is to enable the appropriate interrupt flag
instead of polling the SSD registers.
42.6.4 Stepper Motor Transition Considerations
42.6.4.1 SSD Phase-In and Phase-Out
Prior to starting the SSD flow the SM gauge is usually moved in the proximity of the expected stall position
using another SM driver module. To change the driving source of the SM without visible interruption to
the SSD block it is essential for the user to replicate the coil drive setting valid at the end of the SM drive
into the SSD CONTROL register. Given that the transfer of the port control from the previous SM driver
module to the SSD block can be done sufficiently fast the SM will not move but will start at a know
position with the SSD flow.
The same applies to the end of the SSD flow when the SM control is transferred to another module. It is
essential for the application in this use case that the coil drive setting at the end of the SSD flow is
replicated in this other module.
Basically the seamless hand over of the SM coils to another block can be handled by appropriately
programming the STEP bits and the ITGDCL bit in the CONTROL register prior to pass pad control to
the SSD block. This ensures that one of the SM coils is driven and the SM retains its position when the
SSD block gets pad control.
Vice versa the STEP and ITGDCL setting at the end of the last BIS where the gauge stall was detected
allow the user to replicate this specific coil drive setting to the module taking over pad control from the
SSD block.
For more details refer to specific application notes describing the usage of the SSD block.
42.6.4.2 Changing of SSD Internal States
Depending from the application it may be required to lock the SM into the current angular position to
prevent occasional movement prior to the next step. This is especially useful after the integration phase of
a BIS. To achieve this the internal logic of the SSD block does the following after the integration phase
has expired:
• The coil drive setting of the integration phase is held active: The ITGDCL bit determines the coil
drive; the coil and coil direction is determined by the STEP bits.
• The undriven coil is set (back to) recirculation like in the blanking phase.
This leaves both coils in a well-defined state, nevertheless the user should keep this time outside of the BIS
as short as possible to avoid visible interruptions of the gauge movement.
When changing to the next step within the SSD flow it should be noted that the update of the STEP bits
should coincide (done in the same write to the CONTROL register) like the trigger of the BIS by writing
1 into the TRIG bit. This ensures seamless changeover from one step to the next as well as immediate start
of the BIS when the coil driven has changed.
PXD20 Microcontroller Reference Manual, Rev. 1
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