MC9S12HZ256 Datasheet, PDF (302/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 10 Stepper Stall Detector (SSDV1)
Table 10-11. Return to Zero Modes
0
0
Blanking with no drive
0
1
1
0
1
1
Blanking with drive
Conversion
Integration
10.4.1.1 Blanking with No Drive
In blanking mode with no drive, one of the coils is masked from the sigma-delta converter, and if RTZ is
enabled (RTZE = 1), it is set up to recirculate its current. If RTZ is enabled (RTZE = 1), the other coil is
disconnected to prevent any loss of flux change that would occur when the motor starts moving before the
end of recirculation and start of integration. In blanking mode with no drive, the accumulator is initialized
to 0x0000 and the converter is in a reset state.
10.4.1.2 Blanking with Drive
In blanking mode with drive, one of the coils is masked from the sigma-delta converter, and if RTZ is
enabled (RTZE = 1), it is set up to recirculate its current. If RTZ is enabled (RTZE = 1), the other coil is
driven. In blanking mode with drive, the accumulator is initialized to 0x0000 and the converter is in a reset
state.
10.4.1.3 Conversion
In conversion mode, one of the coils is routed for integration with one end connected to the (non-zero)
reference input and the other end connected to the integrator input of the sigma-delta converter. If RTZ is
enabled (RTZE=1), both coils are disconnected. This mode is not useful for stall detection.
10.4.1.4 Integration
In integration mode, one of the coils is routed for integration with one end connected to the (non-zero)
reference input and the other end connected to the integrator input of the sigma-delta converter. If RTZ is
enabled (RTZE = 1), the other coil is driven. This mode is used to rectify and integrate the back EMF
produced by the coils to detect stepped rotary motion.
DC offset compensation is implemented when using the modulus down counter to monitor integration
time.
10.4.2 Full Step States
During a return to zero (RTZ) event, the stepper motor pointer requires a 90° full motor electrical step with
full amplitude pulses applied to each phase in turn. For counter clockwise rotation (CCW), the STEP value
is incremented 0, 1, 2, 3, 0 and so on, and for a clockwise rotation the STEP value is decremented 3, 2, 1,
0 and so on. Figure 10-10 shows the current level through each coil for each full step in CCW rotation
when DCOIL is set.
MC9S12HZ256 Data Sheet, Rev. 2.04
302
Freescale Semiconductor