Stepper Stall Detector (SSDV1) Block Description
MC9S12XHY-Family Reference Manual, Rev. 1.01
Freescale Semiconductor
707
l
NOTE
A change in the accumulator sample frequency will not be effective until the
ITG bit is cleared.
Table 21-8. SSDCTL Field Descriptions
Field
Description
7
RTZE
Return to Zero Enable — If this bit is set, the coils are controlled by the SSD and are configured into one of the
four full step states as shown in
Table 21-6
. If this bit is cleared, the coils are not controlled by the SSD.
0 RTZ is disabled.
1 RTZ is enabled.
6
SDCPU
Sigma-Delta Converter Power Up — This bit provides on/off control for the sigma-delta converter allowing
reduced MCU power consumption. Because the analog circuit is turned off when powered down, the sigma-delta
converter requires a recovery time after it is powered up.
0 Sigma-delta converter is powered down.
1 Sigma-delta converter is powered up.
5
SSDWAI
SSD Disabled during Wait Mode — When entering Wait Mode, this bit provides on/off control over the SSD
allowing reduced MCU power consumption. Because the analog circuit is turned off when powered down, the
sigma-delta converter requires a recovery time after exit from Wait Mode.
0 SSD continues to run in WAIT mode.
1 Entering WAIT mode freezes the clock to the prescaler divider, powers down the sigma-delta converter, and
if RTZE bit is set, the sine and cosine coils are recirculated via VSSM.
4
FTST
Factory Test — This bit is reserved for factory test and reads zero in user mode.
1:0
ACLKS
Accumulator Sample Frequency Select — This field sets the accumulator sample frequency by pre-scaling
the bus frequency by a factor of 8, 16, 32, or 64. A faster sample frequency can provide more accurate results
but cause the accumulator to overflow. Best results are achieved with a frequency between 500 kHz and 2 MHz.
Accumulator Sample Frequency = f
BUS
/ (8 x 2
ACLKS
)
Table 21-9. Accumulator Sample Frequency
ACLKS
Frequency
f
BUS
= 40
MHz
f
BUS
= 25
MHz
f
BUS
= 16
MHz
0
f
BUS
/ 8
5.00 MHz
3.12 MHz
2.00 MHz
1
f
BUS
/ 16
2.50 MHz
1.56 MHz
1.00 MHz
2
f
BUS
/ 32
1.25 MHz
781 kHz
500 kHz
3
f
BUS
/ 64
625 kHz
391 kHz
250 kHz
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