Stepper Stall Detector (SSDV1) Block Description
MC9S12XHY-Family Reference Manual, Rev. 1.01
710
Freescale Semiconductor
This 16-bit field is signed and is represented in two’s complement. It indicates the change in flux while
integrating the back EMF present in the non-driven coil during a return to zero event.
When ITG is zero, the accumulator is initialized to 0x0000 and the sigma-delta converter is in a reset state.
When ITG is one, the accumulator increments or decrements depending on the sigma-delta conversion
sample. The accumulator sample frequency is determined by the ACLKS field. The accumulator freezes
at 0x7FFF on a positive overflow and freezes at 0x8000 on a negative overflow.
21.4
Functional Description
The stepper stall detector (SSD) has a simple control block to configure the H-bridge drivers of a stepper
motor in four different full step states with four available modes during a return to zero event. The SSD
has a detect circuit using a sigma-delta converter to measure and integrate changes in flux of the
de-energized winding in the stepping motor and the conversion result is accumulated in a 16-bit signed
register. The SSD also has a 16-bit modulus down counter to monitor blanking and integration times. DC
offset compensation is implemented when using the modulus down counter to monitor integration times.
21.4.1
Return to Zero Modes
There are four return to zero modes as shown in
Table 21-11
.
21.4.1.1
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.
21.4.1.2
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.
Table 21-11. Return to Zero Modes
ITG
DCOIL
Mode
0
0
Blanking with no drive
0
1
Blanking with drive
1
0
Conversion
1
1
Integration
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